Change Log for PreonLab

This file is a documentation of all notable changes to PreonLab.

[6.1.3] - 2024-04-10

Fixed

• Fixed a crash in the CSV export of the “Wetting Sensor” if track wetting time is not enabled.
• Fixed an issue that dynamically generated solid particles were not rendered correctly in all cases when using the show particles option.
• Introduced a statistic that displays the number of solid particles per GPU for the scene.
• Addressed a particle deletion issue occurring for very high time step ratios in VSM co-simulations by extrapolating intermediate vehicle states.
• Fixed an MPI VSM co-simulation issue that occurred when reusing a scene.

Optimized

• Reduced the file size of the CUDA plugin.
• In case of a fatal error, the error message is now additionally printed to the terminal. Previously, it had only been printed to the log file.

[6.1.2] - 2024-03-08

Added

• Added support for node-locked GPU licenses.

Fixed

• Fixed an issue that CPS coarsening could fail on the GPU in some cases.
• Fixed an issue where the FFmpeg file path in the User Preferences could not be restored on PreonLab startup.
• Fixed an issue in the “Force Sensor” where use surface normals was not considered on generating the data to be exported to CSV files or buffers.

[6.1.1] - 2024-02-14

Fixed

• Fixed an issue that in rare cases, NaN (not-a-number) values were produced by the PreonSolver on GPU, leading to massive particle deletion.
• Fixed an issue that could lead to a very small timestep for thermal simulations including heat flux boundary conditions.
• Prevented a warning about an invalid nullptr parameter when entering the Scale transform mode with no object selected.
• Fixed a crash in the Connection Editor which occurred when clicking control elements while drawing a new connection.

[6.1.0] - 2024-01-30

Added

Physics:

• Added convective boundary condition for solid objects that interact with thermal solvers.
• Thermal solver: Added the option to choose the implicit solver type. Options are BiCGStab (new default) and CG.

GUI:

• Volume sources: Added the possibility to mesh and export a bad path, if it exists, through a right-click action.
• Added the possibility to export multiple videos at once in the “Video Export” dialog.
• The column separator in CSV exports can now be specified in the user preferences.

Miscellaneous:

• Preon Mesher: Added the ability to set an individual frame rate that also allows for matching the individual frame rate of the connected solver.
• Added Wayland support on Linux.
• Added --gpuSelection parameter to select which GPUs should be used for the calculations.
• Added support for a new GPU Single Node Unlimited license type in the respective CLI, PreonPy APIs, and PreonLab UIs.
• Added a file to the scene folder containing the version of PreonLab it has been saved, simulated, or post-processed with.
• Added a storage category for log files.
• Added a unit option for mesh export of pathlines.

PreonPy:

• Added a get_image method to objects of type FloatFieldObject that allows to get the texture data.
• Added a get_texture3d method to rigids that allows to get the coloring texture data, e.g., when a force sensor is connected.
• Added the do_not_load_resources parameter when opening a scene. This allows opening a scene without resources that might take a long time to load, e.g., geometries, pathlines, or air flow data. To be able to load this data later, a load_initial_resources method was added to the scene.
• Added preonpy.plugin_args(…) interface as a way to pass configuration to plugins. This can be used to select which GPUs should be used for the calculations.
• Added support for Python 3.12.

GPU:

• Added support to combine multiple GPUs within one node to perform a simulation run. All GPUs within a node are employed by default, provided it is covered by a respective license.
• “Air Flow” objects are now supported. For CSV data, the Gridless storage option must be used. For volumetric Ensight data, the VolumeData_Resampled storage option must be used.
• “Car Suspension Model” objects are supported.
• “Snow Solver” objects are supported.
• Tensor fields (e.g., for non-uniform thermal boundary conditions) can now be connected to solid objects that have dynamic sampling enabled.
• The experimental “Void Solver” is supported.
• Windows is not a supported platform for simulation with multiple GPUs. We only use a single GPU in that case.
• The property dynamic sampling of solid objects is supported.
• The option continuous particle size of “Preon Solver” objects and “Solid Volume Solver” objects is supported. This includes adaptive sampling, refinement and coarsening. Refinement domains on the GPU only support refine_continuous. Note that “Pathlines” objects do not work with refinement and coarsening on GPU in this release.

Sensors:

• Added HTC statistics to the thermal sensor for convective BC mode.
• Added column for temperature and HTC measured by thermal sensor for CSV export with convective BC.
• Pathlines: Added the possibility to show directions using equidistant arrows.

Optimized

Solvers:

• Preon Solver: Reduced the GPU memory consumption when gradient correction is set to on.
• Improved the performance on GPU in scenes with many moving solids with varying boundary particle counts.
• Improved the robustness of the thermal timestep limit computation in cases of high thermal boundary condition parameters.

Snow solver:

• Improved the preconditioner in scenes containing several “Snow Solver” objects that differ in hardening coefficient, Young modulus or Poisson's ratio values. This reduces iteration numbers and thus improves performance.

GUI:

• Improved visibiliy and readability of the global coordinate axis.

Miscellaneous:

• Reduced memory consumption when simulating on the GPU by up to 10%.
• Improved scene loading speed considerably for scenes with a lot of pathlines.

PreonPy:

• Improved performance when accessing the statistics of an object with statistics.

Changed

Solvers:

• Changed the timestep of a “Preon Solver” in combination with an experimental “Void Solver” to be more conservative in case the particle size property differs or continuous particle size is used.
• Solid Volume Solver: The maximal timestep property is not automatically adapted anymore due to changing the spacing of the solver. Furthermore, the default value has been changed to 0.02 in a new scene.
• The maximal timestep is internally limited to the smallest frame time interval defined via simulation frame rate (Scene object) or individual frame rate (object supporting this property).

Sensors:

• Quantity names for the CSV export of mesh-based sensors now follow the same naming scheme as statistics.
• For the thermal sensor, renamed the FluidTemperature and SolidTemperature outputs to Reference Temperature.
• The “Thermal Sensor” now always returns a positive value for heat transfer coefficients.
• For the “Thermal Sensor”, renamed the property global fluid temperature to global reference temperature.

GUI:

• In the Plot Dialog, the range start/end properties are not editable anymore if auto update is enabled.
• In the Plot Dialog, the right click action for copying the PreonPy name for multisequence statistics (e.g., “Position”) can now be found on the statistic entry (e.g., “Position”) instead of the sequence entry (e.g., “Position X”).
• In the “Video Export” dialog, specify playback speed instead of input framerate, and start time and end time instead of start frame and end frame. Furthermore, videos of type mp4 remain the only file type available for export.
• FFmpeg File has been moved to user preferences and is no longer in the “Video Export”
• The position marker of the color gradient in the OSD stays visible in case the minimum or maximum of the coloring range is reached.

Miscellaneous:

• The wall function property thermal is only visible now if the thermodynamics boundary type is set to temperature.
• Cameras now have the orientation constraint property that replaces and extends the previous fixed view axis property. It also now allows fixing the viewing direction of the camera, which is enabled by default for orthographic cameras.
• Removed inconsistencies in the naming of the coloring property and the respective label of the color gradient legend for solvers and sensors.
• Object types now follow a common naming scheme, with each word starting with a capitalized letter.
• The scale dragger tool now only has x-axis and z-axis draggers for 2D objects, and the value of the y component of the scaling vector cannot be modified by the user. The dragger for the area source has been modified to only have y-axis and z-axis draggers for a flat jet area type and only a y-axis dragger for a conic one.
• Tensor Field: A re-sampling is now triggered automatically if the field itself or its connected “Tensor Field Box” are transformed.
• The “Tensor Field Box” takes into account the rank when connected to multiple air flows.
• Synchronized the labels shown for the values of the picked particles and the color gradient legend.

Solids:

• The option adaptive sampling is now available without activating dynamic sampling and is supported on GPU.
• The dynamic sampling property of solids (enabled by default) is now supported on GPU.
• Renamed the buffer Thermal Sensor: Solid Temperature to Thermal Sensor: Temperature.
• Added the prefix Boundary Condition: to the boundary condition buffer names (ex: renamed Temperature to Boundary Condition: Temperature).

PreonPy:

• The names_of_measured_values() method for sensors now excludes quantities for which it is known that they are currently not available.
• The Scene.create_object method now accepts the typename parameter in the new common naming scheme, where each word starts with a capitalized letter. Old names will continue to be accepted for some time to ensure a smoother transition.
• Removed the deprecation warning when Object.get_connected_objects(…) or Object.get_connection_slots(…) were called without setting include_target_slot_name to True. We don’t plan to change the default value in future versions.
• We now disallow the setting of arbitrary attributes in the preonpy module. This mainly prevents the use of misspelled attribute names.
• Changed the default value of as_scalars of the PreonPy method Object.statistic_buffers(…) to be False. Therefore, scripts that do not specify that parameter will behave the same as in version 7.0 when it is removed.
• The export_mesh() method for pathlines now allows specifying an export unit. The default export unit is meters.

Libraries and 3rd party components:

• Added the svd3 library to be used in our solver code. Notice the license files included with the installation.
• Updated the Qt library from 5.15.2 to 6.5.3. This license did not change.
• Updated the CUDA version from 11.7 to 12.1.1 used by our CUDA plugin. The licenses did not change.

Deprecation notices:

• The Full license was renamed to the Base license in version 6.0. Starting with version 7.0, the PreonPy API and the PreonCLI and PreonNode command-line interfaces will remove support for the old naming scheme.
• The parameter as_scalars of the PreonPy method Object.statistic_buffers(…) is deprecated and will be removed in version 7.0.
• The parameter load_only_object_creations of preonpy.Scene(…) is deprecated and will be removed in version 7.0. Please consider using do_not_load_resources instead.
• Passing a parameter other than scene_path as a positional argument to preonpy.Scene(…) is deprecated. Starting with version 7.0, such a parameter will only be accepted as a keyword argument.
• The PreonPy property preonpy.current_scene has been deprecated since version 5.0. It will be removed in version 7.0. Please use get_scenes() and preonlab.current_scene instead.
• The PreonPy property preonpy.show_progressbar has been deprecated since version 5.2. It will be removed in version 7.0. Please use preonpy.show_progress instead.
• Support for loading scenes that are created with a version below 2.0 is deprecated.

Fixed

Solvers:

• Fixed issue that the stopping criterion for the position correction solver was not evaluated correctly in all cases when using CPS in combination with the option prioritize fine particles.
• Fixed an issue in the “Solid Volume Solver” where particles would be deleted by a deletion domain, causing a mismatch between serialized static positional data and transient thermal data.
• Thermal solver: Fixed a potential issue in the timestep estimation when thermal timestep limiter was set to diffusivity and CPS was enabled.
• Fixed timestep computation for scenes containing multiple experimental “Void Solvers”.
• Fixed that a “Void Solver” could reduce the timestep of a “Preon Solver” even when the property Time Stepping->adaptive of the “Preon Solver” was set to off.
• Fixed that enabling continuous particle size could reduce the timestep of a “Preon Solver” even when its property Time Stepping->adaptive was set to off.
• Fixed an issue for the position correction solver in cases where the Time Stepping->adaptive property was set to false.
• Fixed an issue where the Avg. Velocity statistic was not computed correctly.

Snow Solver:

• Fixed a regression in which friction was applied twice, once explicitly and once implicitly. Legacy scenes that suffer from this regression will give you a warning and still apply the friction twice, so that the behavior will not change with PreonLab 6.1. New scenes will only apply it implicitly.
• Fixed an issue where adding two “Snow Solver” objects to a scene would make the unsupported property continuous particle size appear in one of the solvers.

GUI:

• Fixed an issue in the property editor that some numerical properties rejected the value 0 as input if several objects had been selected.
• The name property of periodic boundary solvers is now editable in the property editor.
• Fixed an issue that the GUI could end up in an invalid sceneless state when opening a legacy scene and not opting for converting it.
• Fixed that in the Plot Dialog, the plot range properties could not be adjusted manually while simulating.
• Fixed an issue in case thermodynamics was disabled but temp. based viscosity was still enabled.
• The lines of the grid shown in the OpenGL window now keep their thickness regardless of the zoom level of the camera.
• Fixed that some objects returned by preonlab.selection() did not work correctly.
• Fixed a potential crash when executing scripts in the PreonLab Console.
• Fixed an issue in the Plot Dialog where the labels of the time axis were distored on some occasions.
• Fixed a bug where, in certain situations, the undo/redo buttons weren’t disabled during property editing.
• Fixed an issue where expanding a box in the Connection Editor would not paint it on top of all the (now) overlapping other boxes.
• Fixed an issue in the property editor where an outdated tooltip was displayed for properties with no value.

Miscellaneous:

• The value given by memory statistics now correctly matches the provided unit. Previously, the value was stated as given in MB but was actually given in MiB.
• Preon Mesher: Fixed an issue in the “Mesh sequence” right-click action that occurred if the connected solver used an individual frame rate for serialization.
• Pathlines: Fixed an issue in the “Generate Pathlines” right-click action that occurred if individual frame rate was enabled.
• Fixed an issue where, in some cases, PreonCLI/PreonNode started simulating on the CPU even if a GPU simulation was requested.
• Pathline mesh export: Fixed an issue with normals that would point inward the generated mesh and reduced the number of generated triangles in the exported mesh.
• Fixed various minor legacy loading issues.
• Removed noisy output when canceling a simulation in PreonCLI.
• Fixed the Time Step and Min. CFL Time Step statistics, which were logged with an offset of one simulation step.
• Fixed an issue with “Heat Field”, “Volume Sensor”, and “Box Domain” objects that would not update their volume of interest after substituting the connected mesh that would limit this volume.
• When exporting meshes on Linux systems, the file extension of the type selected in save/export dialog is now automatically added to the filename.
• Fixed an issue where particles got refined before being inside very narrow cylindrical domains.
• Fixed the Cum. Update statistics in the OSD, which used to take account of the simulation time only after it was logged.
• Fixed an issue if “Apply connected tensor field” was applied to a solid in a scene where this was done before but the connection between tensor field and solid was not saved.
• Fixed an issue that could lead to particle leakage after scene reload of a solid with adaptive sampling enabled and connected to a sensor collecting per-particle data (e.g., by enabling track max pressure in the “Force Sensor”).
• Fixed an issue in the Action Log messages regarding the “Set all sub-properties to their default values” action.

PreonPy:

• Fixed exception raised when accessing statistics on a scene with load_only_object_creations=True. Now, preonpy.DataNotAvailable is raised instead of a TypeError.
• Fixed an error that Statistic.display_unit could be set to units incompatible with the base unit of the statistic.
• Fixed crash in Object.get_parent_group().
• Fixed an error in Object.statistic_buffers(…) in case the object contains an Euler-angles statistic.

GPU:

• Fixed an issue where serialized temperature data of a “Solid Volume Solver” would be loaded into CPU memory but not into GPU memory when reloading a scene.
• Fixed a performance issue in the thermal solver caused by an increased number of simulation steps when compared to the simulation run on the CPU.
• Fixed an issue for multiphase simulations where the statistics for implicit viscosity had only been written to the first solver.
• Fixed an issue with boundary handling for implicit viscosity when the solid had a roughness value different from the default one.
• Fixed an issue where the positions of particles of the “Solid Volume Solver” would not be updated after a simulation step.
• Sensor plane: Fixed an issue where statistics would not update properly during simulation in case a “Solid Volume Solver” was connected.
• Fixed an issue that occurred on simulation start in case an inactive solver was connected to a “Sensor Plane”.
• Fixed an issue where the “Thermal Sensor” would not be notified about a change in Wall Function -> thermal of a solid object.
• Fixed the issue that the “Solver Particles” statistic of the scene was only updated at full frames in GPU simulations.
• Fixed a GPU vs CPU discrepancy in the Drag Force model.
• Fixed a GPU vs CPU discrepancy in thermal simulations that affected velocity-scripted particles.
• Fixed a GPU vs CPU discrepancy related to velocity-scripted particles of the Preon Solver.
• Fixed an issue where a “Transform Group” connected to an inactive “Solid Volume Solver” would trigger an exception.
• Fixed an issue when improved RJ is turned off.

Preon Renderer:

• Fixed a rare crash when rendering sensor planes.

Removed

Solvers:

• Removed that default connections were drawn between a “Solid Volume Solver” and a “Box domain” or an “Outflow domain”.
• Removed the maximal timestep property of the “Void Solver” that unintendedly influenced the “Preon Solver” timestep in rare cases.
• Removed the unusable input slot “ThermalPower” from the “Void Solver”.

Sensors:

• Removed the statistic Culled Non-surface Particles from the “Height sensor” since it was only intended for internal use.

PreonPy:

• Removed the old API for retrieving statistic information (including methods get_statistic(…), get_statistic_avg(…), get_statistic_min(…) and get_statistic_max(…)). Please use the new Statistic API, which can be reached via Object.statistic(…).
• Removed the 6.0 part from the legacy property name mapping.
• Removed usage of the mprop library.
• Removed support for Python 3.7.

[6.0.3] - 2023-09-26

GPU:

• Fixed an issue that could cause deviations from results achieved on CPU for thermal simulations that had boundary condition set to heat flux in solids.
• Fixed an issue that the “Force sensor” measured incorrect values when enabling gradient correction in the “Preon Solver”. Also fixed a possible crash caused by the “Force sensor” related to this issue.
• Fixed an issue that an exception was thrown when simulating a scene with an inactive solver that was connected to a domain.

Miscellaneous:

• Fixed a performance issue that a “Vector field visualizer” connected to non-transient airflows were updating in every simulation step.
• Fixed a crash that could occur in sensors with a cell size in cases the number of generated cells was too high to fit into RAM or resulted in a texture too big to display by introducing the property cell limit.

PreonPy:

• Fixed a crash when using PreonCore objects that already got deleted in the scene. The bug occurs only if the scene was opened with GPU support. Furthermore, it only affects objects of type “Preon Solver”, “Solid Volume Solver”, “Drag Force” and “Heat Field”. Now a preonpy.ObjectInvalid exception is thrown when using them.
• Fixed a crash when using a Statistic object whose associated simulation object has been deleted from the scene.

PreonNode:

• Removed erroneous output Feature "Internal" is enabled. logged by every node except the first one.

[6.0.2] - 2023-08-22

• Fixed the issue that the “Vector field visualizer” would not reflect the updates within a transient air flow in case the simulation is run headless, i.e. via PreonCLI, PreonNode or via PreonPy.
• Fixed a regression in the “Thermal sensor” in cases where ignore dry areas was enabled.
• Fixed extremely rare endless loop that could occur when loading a .prstate file.
• Fixed the --continue command-line argument when starting simulations with PreonCLI.
• Fixed a crash that occurred when exporting a mesh containing texture coordinates.
• Prevented a crash that occurred in multiphase simulations on GPU in which the property implicit viscosity were not synchronized across solvers. This is now checked and prevented by the GPU compatibility check.
• Fixed emission issue that occurred in 2D and 1D simulations on GPU.
• Fixed a legacy loading issue, where either a scene object’s property or a statistic display unit had a rotational velocity unit entry with its value set to rpm (rotations per minute).

[6.0.1] - 2023-07-26

Miscellaneous:

• Fixed a crash that could occur when trying to set a new default scene directory in the User Preferences with the currently set default directory not existing.
• Fixed an issue that the default scene directory has not been created on fresh installations of PreonLab.
• Removed the minimum size requirement from the dialog of the installer which could cause problems on small displays.

GPU:

• Fixed the issue that a simulation could not be started on the GPU if the behaviour property of a “Preon Solver” object was set to inactive.
• Fixed an issue that simulations with continuous particle size could not be continued. Continuous particle size on the GPU in 6.0 does not feature refinement and coarsening.
• Fixed an issue that the CFL timestep was too low when continuous particle size was on. Continuous particle size on the GPU in 6.0 does not feature refinement and coarsening.
• Fixed an issue that implicit viscosity would not use the correct timestep.

[6.0.0] - 2023-07-03

Added

General:

• Added support for GPU-accelerated simulations using CUDA. Please note that only a subset of features is currently supported on the GPU. When starting a GPU simulation, PreonLab will give feedback if the scene requires features that are not available on the GPU yet.

Physics:

• Added the experimental lateral adhesion force for modeling droplet sticking and run-off more realistically.

Sources:

• Added the property allow adaptive filling to the “Volume Source”. If enabled and if the receiving object uses CPS, the source may emit coarser particles inside the volume. This option is only available when using the quality fill method.
• Fixed an issue where the Emitted Volume statistic from the “Area Source” was sometimes reset to zero when resuming a simulation.
• Added Velocity and Volume Flow Rate statistics to the “Area source” object.

GUI:

• Added the possibility to copy images from the graphics window or renderer dialog by adding copy icons to their respective toolbars.
• Added the ability to close a scene.
• Added the right-click action “Check GPU compatibility” to the “Scene” object in order to check whether a scene is eligible for simulation on the GPU with the currently supported feature set.
• Added right-click actions to open directories for the scene, statistics, CSV files and simulation data, if present. They are grouped into the “Open location” sub-menu.
• Added a switch to also consider the name of groups when searching for a property in the property editor.

Sensors:

• Pathlines: Added the possibility to mesh and export the pathlines in the chosen format through a right-click action.
• Volume sensor: Added a property compression that will display the sampled compressed volume for compressible solvers if turned on. Compressible solvers are the “Snow solver” and the “Preon Solver” with implicit equation of state enabled.

Miscellaneous:

• PreonCLI: Added a --continue parameter that allows a previously canceled or otherwise stopped simulation to be continued based on the last written scene statistics.
• PreonCLI/PreonNode: Added a --featureOnGPU parameter for activating the GPU support.
• Added a right-click action to export one or multiple solid geometries as a single mesh file.
• Added Deleted Particles, Scripted Particles and Cum. Deleted Particles statistics to the “Box domain”, “Outflow domain” and “Maximum velocity condition” domain objects.
• Added a GPU Memory statistic to the “Scene” object, which tracks the amount of memory spent while simulating on the GPU. Note that this does not account for memory spent on visualization (e.g., rendering).

PreonPy:

• Add support for Python 3.11.
• Added statistic.sequences for querying all the sequences of a statistic as StatisticSequence objects. Those allow for querying and setting sequence properties like the color.
• Added preonpy.LicenseTypes.GPU to be used in preonpy.checkout_license(...) calls and to be returned in preonpy.get_license() calls.
• Added .values() and .items() accessor methods to buffer sets.
• Added export_mesh() for preonpy.Pathlines that meshes and exports the pathlines to a 3D file.
• Added preonpy.set_features to enable and disable features. This is currently mainly used to enable GPU usage when PreonPy is used as a package within a user-provided Python environment, e.g. without using PreonCLI.

Optimized

GUI:

• Optimized in which scenarios the “Set/Remove (Transform) key” actions are provided.
• Optimized the coloring of keyframed properties in the Property Editor.
• When selecting an object, the Scene Inspector will scroll automatically to the respective entry in the scene tree.
• Optimized the layout of property tooltips.

Changed

Preon Solver:

• Removed density-based coloring because it only gave correct results when used during the simulation.
• Statistics include the average velocity now in addition to minimum and maximum velocity.

Snow solver:

• Removed clamp pressure property.
• The property dynamic sampling is not visibile anymore when choosing Impulse Boundary Handling as it is always off in this case.
• Removed Wall function property group.
• Removed coloring options not related to the “Snow solver”.

GUI:

• Picking particles of downsampled solvers is prevented now, as they have no direct simulation data attached to them.
• Renamed the licensing dialog menu item to “Licensing” and moved it to the “Settings” menu.
• In the Property Editor, it is now possible to directly edit the strings of vector-like properties.
• The right-click actions “Compute axis from points” and “Set temperature” now ask for input values in the respective default unit defined in the “Scene” object.
• On startup no empty scene will be created anymore.
• On scene load or scene creation, a progress bar is shown for as long as it takes to not only load the scene but also load additional plugins. The loading time for certain plugins, e.g., the GPU plugin of PreonLab, may take longer when called for the first time.
• The export of particle data to the EnSight Gold format is now universally available to all particle solver types (e.g. “Preon Solver”, “Snow Solver”, “Solid Volume Solver”).
• Critical error messages are now always printed in the message window.
• Changed the default target directory for export dialogs from the PreonLab installation directory to the current scene directory.
• Heat Field: The properties power and volumetric power are not shown anymore as soon as a “Point Cloud Resource” providing respective quantity is connected via the TensorField slot.
• Renamed the “Memory consumption” dialog, located under the “Help” menu, to “System memory consumption”. For tracking GPU memory usage, please refer to the GPU memory statistic of the Scene object.
• Renamed the per-object “Memory” statistic to “System Memory”.

Sources:

• Fixed the issue that an “Area Source” with seedpoint filling could script the particles of other overlapping sources.
• The script nearby particles option for an “Area Source” now only scripts particles in front of the source.
• Fixed flow rate for PipeFlow the “Area Source” so that the emitted volume matches the one expected.

Sensors:

• Force Sensor: Added a toggle use rigid normals to only consider the normal components of the forces applied by the fluid particles to compute pressure forces and torques.
• Deleted particle visualizer: Changed the name of property scale to particle scale to avoid ambiguities with the scale transformation property.

Solids:

• The rotational velocity of scripted solids can now be specified in different units. For that, the property revolutions per second has been renamed to rotational velocity, and the value for it can be specified in all rotational velocity units, including rps and rpm.
• Removed coloring options number density, mass contribution and memory location.

MPI:

• Added workaround to avoid out of memory issue that could occur with some MPI implementations during dynamic boundary sampling.

Miscellaneous:

• Air Pressure: The keyframes for distance-based air pressure mapping now have to be stored in the air pressure (distance) property to avoid time-based evaluation in case dist. based air pressure is disabled.
• Preon Solver: The keyframes for temperature-based shear and bulk viscosity mapping now have to be stored in the shear viscosity (temperature) and bulk viscosity (temperature) properties to avoid time-based evaluation in case temp. based viscosity is disabled.
• In case PreonCLI/PreonNode is called with --lBoost=sim_threads_max and not enough licenses are available to cover all threads, it will cancel with an error message. In earlier releases, only a warning was printed, and the simulation started with fewer simulation threads than the system would provide. The user should specify the exact number of additional simulation thread licenses to cover the whole machine (e.g., --lBoost=10).
  
• Better handling in case the environment variable OMP_NUM_THREADS is set to a value that is higher than the number of available cores. As before, the number of actually used threads will be reduced to the number of available cores. But now a warning is logged, and the number of simulation thread licenses requested will align with that number.
• Renamed the unit category angular velocity to rotational velocity.
• Updated the MSVC redistributable shipped with PreonLab. If PreonLab is being used as a pre-installed package on Windows, it should be made sure that the redistributable is manually installed. It is located under the vcredist sub-folder of the pre-installed PreonLab package.
• The min/mid/max color range properties are now given in the unit that is selected in the respective unit property.
• The import of keyrames and statistics now auto-detects and supports the following delimiters: “;”, “,”, “:”, “|”, ” “,”0x09” and “~”.
• The Full license is now called the Base license to better express its extendability with a GPU license or licenses that extend the number of CPU simulation threads in MPI contexts. The renaming is visible in the GUI of PreonLab, but also in the preonpy.checkout_license function of the PreonPy API and in the -licenseMain argument of PreonCLI/PreonNode.
• Removed the possibility to create Statistic resource objects from the Add->Resource menu. Such objects can still be added using the File->Import->Import Statistics entry or by dragging & dropping the resource file.

PreonPy:

• The function statistic_names() will now return the names of all statistics, even if they have no data available. Furthermore, the function will only return one statistic name per vector-valued statistic. Example: Only Linear Velocity will be returned instead of Linear Velocity Norm, Linear Velocity X, Linear Velocity Y and Linear Velocity Z.
• Methods that take a physical argument as parameter now also allow passing a Quantity object.
• The function Scene.find_object now returns the Scene object (in other words, it returns itself) if it is called with "Scene". This is to allow the user to check in a generic way if a name could be used by a new object.

Libraries and 3rd party components:

• Updated the pybind11 library which powers our PreonPy Python bindings from 2.9.0 to 2.10.1 in order to support Python 3.11. This license did not change.
• Our CUDA plugin includes the following open source software: LLVM, lz4 and PCRE. Notice the license files included with the installation.

Fixed

Preon Solver:

• Fixed a bug in the Herschel-Bulkley viscosity model that prevented a buffer from being created when switching the viscosity model while simulation data was already present.

GUI:

• Fixed a bug where sometimes the “Messages” tab was not resized when the message count changed.
• Fixed a bug in the Property Editor that for strings containing several adjacent whitespace characters, only a single whitespace has been rendered.
• Fixed a bug in the Plot Dialog image export that caused the plot lines to be slightly offset.
• Fixed a bug in the presets manager that caused misleading warnings about property synchronization to be printed.
• Fixed a bug where two objects were shown as selected in the Property Editor when pasting a single “Area Source”.
• The value of the position marker of the color gradient in the OSD now considers the unit set by the user (e.g., by means of the unit property in the Appearance->Coloring group).
• Fixed that the velocity storage implementation of an “Air Flow” could be keyframed.
• When changing the coloring mode, the min/mid/max color range properties in the Property Editor are now updated immediately.
• Fixed a bug where the OSD had not been immediately updated when changing a Material connection slot.

Sensors:

• Thermal Sensor: Fixed a bug where per-particle time-averaged quantities would ignore the state of the property ignore dry areas.
• Thermal Sensor: Changed the reported value for dry areas on the connected solid from INFINITY to NaN in the buffer access.
• Fixed a legacy loading issue for the “Volume sensor” object when used with an arbitrary mesh in scenes created prior to 5.3, where a fixed value was used instead of one based on the minimum particle size.
• The Velocity projection field and Height field sensors don’t keep the previous OSD values anymore if all particles have vanished from the considered volume.

Rigid body particle solver:

• Fixed a bug that the rigid body particle solver could not recover after throwing an exception.

PreonPy:

• Fixed a potential crash in the preonpy.Object.statistic_buffers export functionality. The crash happened when as_scalars=False was used, where there were some vector-valued statistics (e.g. with an X, Y and Z component) and one of those vector statistics had no value at any point in the statistic time range.

Miscellaneous:

• Fixed a bug where the axis-aligned bounding box of an object would not be updated correctly after modifying its pivot.
• Fixed a bug where existing simulation data could be lost under certain circumstances when saving an untitled scene to a network path from a Windows system.
• Keyframes are now checked to be sorted according to time (or any other key type) when imported from CSV files.
• Fixed an issue for scenes with multiple “Air Objects”, where one thermally active “Air Object” would enable thermal interaction for all “Air” objects in the scene, thermally active or not.
• Fixed an issue that occurred when connecting a “Tensor Field Box” to a scaled “Acceleration Field” in that the box would not filter the field correctly.
• Fixed an issue in the CSV export of statistics of multiple objects at once where the column name would contain duplicate mentions of the object a particular statistic belongs to.
• Fixed a rare issue where user-defined volumes (e.g., in a heat field or volume sensor) classified points as outside when they were actually inside the volume.
• Fixed a bug where disconnecting the TriangleMesh from a “Heat Field” did not reset the volume to the volume determined by its scale parameters.
• Fixed the issue that sometimes a scene could not be opened while it was simulated by another PreonNode, PreonCLI, or PreonLab process.
• Fixed an issue where turning on momentum wall functions on a solid would apply them to all solids. Momentum wall functions are now applied on a per-solid basis.
• Fixed an issue in the export of solver particles to the EnSight Gold format where a frame containing zero particles (e.g., frame 0) would generate warnings in external tools.
• Fixed a crash that would occur if an “Air Flow” object employing volume data tried to query its data structures after loading of the respective input files failed.
• The average temperature statistic of the “Solid Volume Solver” is now mass-weighted.
• Objects other than the scene object now cannot be named “Scene” anymore.

Removed

PreonPy:

• Removed the legacy handling mechanism for the following property renamings: adaptive spacing to continuous particle size, min. spacing to min. particle size, spacing to particle size/max. particle size, coarse particles to coarsen particles and source spacing to particle size. These renamings were introduced in version 5.2.

Deprecation notices:

• The old API for retrieving statistic information (including methods get_statistic(…), get_statistic_avg(…), get_statistic_min(…) and get_statistic_max(…)) will be removed in version 6.1. The new Statistic API, which can be reached via Object.statistic(…), is now recommended to be used instead.

[5.3.4] - 2023-04-28

• Fixed an issue where metered Simulation Thread licenses could not be checked out. Metered licenses got introduced in 5.3. Non-metered licenses are not affected.
• Fixed an issue that in some cases Simulation Threads licenses could not be increased or decreased using PreonPy during application run. License checkout at application start is not affected.
• Fixed an issue with saving a scene containing a multi-file STEP assembly as portable (i.e., mesh files are copied into the scene folder from External Resources).
• Fixed an issue in the transform slot of the “Particle Tracker” where the tracked particle’s position was not considered.
• Fixed an issue that prevented the pathline sensor to be duplicated if one of its dimensions was too small.

[5.3.3] - 2023-03-21

• Fixed an issue in replaying transient air flows after saving and reloading a scene that contains an “Air Flow” object.
• Fixed an issue where a user-specified velocity offset would not be applied to the imported air flow when using Ensight Gold data files and having “Use volume data” enabled on import.
• Fixed possible CPS stability issue caused by “Area Source” emission.
• Fixed an issue with loop keyframes on “option” properties (e.g. behavior) in that the loop keyframe would become invalid after saving and reloading the scene.
• Fixed a bug for statistics resources that the statistics have not been grouped correctly after loading a scene.
• Fixed an issue in mesh-based sensors where connecting them to an inactive solid would lead to a crash when exporting per-sample data.
• Fixed a bug that colors of vector statistics were not restored when opening a scene.

[5.3.2] - 2023-03-03

• Fixed an issue with wall function values for moving rigids.
• Fixed an issue in the computation of the read-only mass property of the “Solid Volume Solver”.
• Fixed an issue regarding the emitted power of a “Heat Field” in case it was applied to a “Preon Solver” with continuous particle size enabled and thermodynamics solved implicitely.
• Fixed an issue regarding the Cum. Emitted Energy of a “Heat Field” where the wrong timestep was applied to convert from power to energy.
• Fixed an issue in point cloud resources where toggling aabb from sample points would only be considered on (re-) importing the resource.
• Fixed an issue where sensors ignored solvers with particle sizes higher than the lowest one. continuous particle size was not affected by this.

[5.3.1] - 2023-01-12

• Fixed a synchronization issue when using a “Void Solver” in an MPI simulation.
• Fixed an issue leading to an increased simulation step update time when using one of the following objects: “Box domain”, “Heat Field”, “Pathlines” or “Volume sensor”.

[5.3.0] - 2022-12-06

Added

GUI:

• Post-processing dialog: The list of objects can now be filtered.
• Added a right-click action for mesh-based sensors to select their corresponding solid objects.
• Added the tab Action Log to the tab bar in the lower right of the main window. It lists all actions stored on the undo/redo stack. The latest action applied to the scene is highlighted here. Furthermore, the action log is saved to the scene folder on saving the scene.
• The unit for the color gradient shown in the OSD can now be changed by means of the unit property in the Appearance->Coloring group.
• The Plot Dialog now shows a tooltip with two kinds of temporal averages when hovering over a graph: Uniform Avg. and Time-weighted Avg.. Uniform Avg. is the arithmetic mean of all sample points without weighting. Time-weighted Avg. takes into account the uneven distributions of the data points in time. This averaging method assigns to each data point a weight that is proportional to the summed time differences between it and its neighboring data points.

Solvers:

• Solid Volume Solver: When the heat capacity modifier is used, the temperature distribution inside a solid may converge faster, making the physical time required to reach this state shorter.
• Refinement and deleted particles history are written to disk every 100 seconds. This prevents loss of data if the simulation is aborted by killing the process.

Sensors:

• Thermal Sensor: Added the possibility to manually define a fluid temperature for the computation of the global heat transfer coefficient.
• Sensor Plane: The sensor plane is now able to measure the mass flow rate and cumulative mass. Added the property MassFlowRate which shows the corresponding coloring.
• Volume sensor: The sensor now additionally measures the mass of the connected fluid.
• Pathlines: Added the possibility to track particles for a range of frames, instead of only a single frame.
• Pathlines: Added the possibility to track particles passing through a volume defined via connected solids. The resolution of the volume discretization is either automatically derived from the min. particle size of the connected solver, or set manually using the new properties manual volume grid cell size and volume grid cell size.

PreonPy:

• Added support for PathLike objects such as pathlib.Path in all places where previously only str was accepted as a path.
• Added the possibility to specify the buffers that should be part of a requested bufferset.
• Added the possibility to extract a particle’s color in the RGBA format.
• Added object.get_property_default() for querying the default value of a given property.
• Added object.keyframe_sequence_names which returns a list of all keyframe sequence names of an object in its current state.
• Added object.get_property_keyframe_sequence_names(property) which returns a list of all keyframe sequence names of the provided property of the object in its current state.
• Added statistic.value_type for querying the type of the data this statistic stores.
• Added statistic.has_data for querying if the statistic currently holds any data.
• Added the parameter as_scalars to object.statistic_buffers. When set to False, vector statistics will be exported as a single buffer containing vector values instead of distinct buffers containing scalar values for each vector component.
• Added object.get_parent_group() for querying the Group to which an object is assigned.
• Added object.is_property_keyable() to test if keyframes can be set for a property. Note that some properties are keyable but not writable, i.e., they require the definition of keyframes for a well-defined usage of the property.
• The statistic.avg() method now has a new optional parameter weight. By default, it is set to WeightMode.UNIFORM, which causes the function to return the unweighted arithmetic mean. Alternatively, it can be set to WeightMode.TIME for time-weighted averaging.

Air flow (with Ensight Gold data files as source):

• Import dialog: Check “Use volume data” to import the volumetric information of unstructured three-dimensional polyhedral types (e.g., hexahedrons). This results in better preservation of the input data.
• Added optimise non-planarity in the “Air flow” object, which reduces interpolation artifacts in cases where the data set contains volumes or cells with non-planar faces.

Miscellaneous:

• The value for the volume grid cell size is now automatically derived based on the minimum particle size of a connected particle provider for the “Heat field”, the “Box domain” and the “Volume sensor” objects. A custom value can be set by toggling the manual volume grid cell size property, which is set to Off by default.
• Added support for metered licenses. Now it is possible to specify the boost license model separately from the main license model for PreonCLI and PreonNode using the --licenseModelBoost command-line parameter and for PreonPy the license_model_boost parameter for the checkout_license function.

Optimized

GUI:

• Improved the performance of the Plot Dialog for statistics with many data points.
• Reduced computational overhead when having the Plot Dialog open while simulating.
• Added the right-click action “Zoom to fit” to objects with a sense of position within the scene.

PreonPy:

• Improved performance of object.statistic_buffers() in case the fixed_time_interval argument is False.

Changed

Vehicle Simulation Model:

• This object type has been changed to be an experimental feature.
• Alleviated the 20 entries limitation in the parameter set property of the “Vehicle Simulation Model”.
• It is now possible to load a scene pointing to a VSM project not matching the loaded API binaries (or redistributables), providing the chance to update the project path. A simulation is only performed in case the VSM project and the loaded API binaries match.
• Removed Clip, ForceField and Distance connection slots.
• Disabled setting the simulation end automatically: The PreonLab simulation will continue although the VSM simulation has ended.

Car Suspension Model:

• Removed Distance connection slots.

Preon Solver:

• It is now possible to use temperature-based density and the CPS Particle Resampling (coarsening and refinement) at the same time.
• For performance reasons, Area sources that emit fluid intersecting geometry are not handled by the CPS system anymore. Resulting instabilities at the outflow must be resolved by adapting the source setup.

GUI:

• The Plot Dialog is now able to simultaneously display statistics from objects with different time samplings without the need to enable fixed step sampling.
• In the Plot Dialog, timings are now hidden by default. They can be enabled by checking the respective check box.
• Removed the warning dialog that would show up when trying to change the simulation frame rate or view frame rate in the scene object or the individual frame rate of, e.g., a sensor on a frame other than zero.
• Thermal sensor: Options for coloring are now limited to the currently available measured quantities.
• Undo/redo actions are now disabled while editing a property.
• The time axis in the plot dialog now automatically chooses a unit that is adequate for the given range. It is also possible to set a specific unit manually.
• Editing a property in the property editor can now be aborted by pressing the “Esc” key.
• “Import Tensor Field” dialog: Labels are now shown to the right of the respective checkbox.
• The “Copy PreonPy name” right-click action is not displayed for properties in the “Scene UI Settings” anymore, since they are not accessible via PreonPy.
• Pathlines: The thinning factor property is visible only if thinning is enabled.

Sensors:

• The FlowRate property of sensor planes has been renamed to VolumeFlowRate.

PreonPy:

• The new preonpy.Statistic interface now supports non-scalar statistics. For example, object.statistic("Position").at(0).value will now return a preonpy.Vec3 object instead of a float value that just contains the norm.
• The preonpy.Statistic.at(time) method will now throw a preonpy.DataNotAvailable exception if the statistic has no data at the given time point. Previously, a RuntimeError exception had been thrown.
• The methods object.get_connected_objects and object.get_connection_slots now have an additional optional argument include_target_slot_name, which is set to False by default. Setting it to True will return a pair for each connected object containing the object as well as its slot name.
• The preonpy.get_license function now returns a fourth tuple element containing the boost license model.

Miscellaneous:

• Thermal sensor: Removed a spacing correction term in the computation of the local heat transfer coefficient in accordance to the formula provided in the manual.
• The right-click action “Apply connected tensor field” can now also be applied to build-in solids (e.g. box). This action is only available if dynamic sampling is disabled.
• In the unit system, the physical quantity heat capacity has been renamed to specific heat capacity and flow rate has been renamed to volume flow rate.
• In cases where the volume of a “box domain”, “volume sensor” or “heat field” is described via connected solids, the re-generation of this volume after transforming these solids is now performed automatically.
• It is not possible to set the scale of an object to 0 anymore.
• The connections DeletionDomain, which connected a domain to a rigid, and RefinementDomain, which connected a domain and a solver, are merged into a single connection called Region, which can connect a domain to both solvers and rigids. This affects the following domains: BoxDomain, CylindricalDomain, MaximumVelocityCondition and OutflowDomain.
• The values of the property types for the domains mentioned above (excluding MaximumVelocityCondition) deleteFluidParticles, deleteRigidParticles, deleteSolidVolumeParticles and deleteAll are unified into a deleteParticles property value. The information to which solver or rigid the domain should be applied is encoded through the Region connection. Per default, a domain is connected with all existing solvers. Connections to existing rigids should be made manually.
• The convergence criterion property of thermodynamics solvers has been renamed to thermal timestep limiter.
• When copying an object, the units and the colors of statistics are now also carried over to the pasted object.
• Preon Renderer: Objects of type “Point Light”, “Directional Light”, “Clipping Plane” and “Camera” are now rendered if visible.
• Removed the render scripted particles property for solvers.
• PreonNode now writes all log messages during startup to the standard output stream.
• If the last used license is not available, a list of all available licenses to pick from is now shown.
• Removed the Distance, Transformation and Clip connection slots from the “MaximumVelocityCondition” object.

PreonNode:

• The statistic “Total Wait Time” now accumulates the time of the node that had to wait the longest each simulation step.
• The simulation is now aborted if a required airflow or vector field file is missing or invalid.

Fixed

PreonSolver:

• CFL number is not shown anymore for fluids that have Timestepping -> adaptive set to off. CFL number is not shown anymore in the “Void Solver” and the “Solid Volume Solver” where it had no effect.
• Fixed that DFV/DIP solver would crash when using CPS or the old multi-solver based fluid refinement system.
• Fixed potential stability issue when using MPI and CPS.
• Fixed possible leakage when sharing the same submesh of a mesh resource in dynamically sampled rigids.

Sources

• Fixed emission issue when using a rotated or translated area source with flat jet or cone area.

GUI:

• In the property editor, when changing a scene’s default unit, the range for properties is now updated accordingly.
• Fixed an issue in the property editor that prevented setting the value of a property to its range minimum when multiple objects had been selected.
• Fixed an issue that the property editor showed some properties erroneously as being keyframed when the Scene object has been part of the object selection.
• Fixed an issue in the property editor that some groups had erroneously been hidden when using the filter functionality.
• Fixed a potential crash when trying to import invalid or empty mesh files.
• The scene is now shown as “modified” also when the unit or the color of a statistic has changed.
• Fixed various vendor-specific issues in the GL rendering.
• Fixed an issue in the keyframe editor where the tooltip would not show the display name of an enumerator property (e.g. behavior) but a number.
• In the Scene Inspector, it is not possible anymore to enter the object renaming mode for static objects.
• In the Scene Inspector, the “Show/Hide all in Group” right-click action is working again.
• Fixed an issue in the “Vector Field Visualizer” where it would update itself more than necessary.

Sensors:

• Fixed that the “Particle Tracker” would always render a particle with max. particle size when using CPS.
• Fixed that “Sensor mesh” and “Sensor plane” do not add “Temperature” to the list of measurable values when enabling thermodynamics in a connected “Preon Solver”.

PreonPy:

• The object.get_connection_slots and object.get_connected_objects methods reference only objects visible in the Scene Inspector.

Tensor Field Import:

• Fixed an issue where valid inputs for transient data were rejected due to floating point inaccuracies.
• Fixed an issue introduced in PreonLab 5.2.4 where the local transformation was not applied to point cloud resources.

Connection Editor:

• Fixed an issue where the connection editor showed/hid slots that should not have been visible/hidden anymore.

MPI:

• Fixed Preon Renderer paticle coloring issue that occurred when using automatic range coloring during an MPI simulation.

Miscellaneous:

• The Scene statistic “Licensed Threads” is now renamed to “Tot. Licensed Threads” and is now also a total of threads over all MPI nodes.
• Fixed an issue in the Plot Dialog with semi-transparent background colors.
• Fixed an issue where a timestep of zero was suggested for an RBPS simulation after a preceding simulation abortion due to an incorrect scene setup.
• Fixed the issue that the “Clipping Plane” object was not rendered correctly if switching the shape type to Box.
• Fixed an issue where pathlines would sometimes erroneously end after coarsening.
• Fixed an issue where the PreonScenes directory was created although a different default scene path was set in the User Preferences.
• When importing an existing .stats file as statistics resource, the original representation of the statistic list is now restored, i.e., vector statistics are grouped again.
• In case both --licenseModel and --licenseBoost command-line options are passed, the chosen --licenseModel is not ignored anymore.
• Fixed determinism issues when resetting simulations to simulation start and simulating again.
• In PreonCLI, if there is only a floating “Additional GUI” and a node-locked “Additional GUI” available and neither --licenseModel nor --licenseMain has been specified, it is now ensured that the node-locked one is chosen.
• Fixed an issue in the Keyframe Editor that could occur when two keyframes would have the same time key and spline interpolation was enabled.
• Acceleration Field: Fixed an issue where the object´s own rotation would not be applied to the imported acceleration vectors.
• Fixed an issue in the export of solver particles to the EnSight Gold format where not all particles would be exported.

Removed

PreonPy:

• Removed support for Python 3.6.

[5.2.6] - 2022-11-09

• Fixed potential leakage when using multiphase, CPS and adaptive boundary sampling.

[5.2.5] - 2022-10-19

Fixed

• Fixed an issue that two-way coupling and CSM/VSM didn’t work correctly when using the old multi-solver based fluid refinement system.
• Fixed an issue that the “Volume Sensor” didn’t use all available CPU cores when sub particle precision was turned on.
• Improved stability when using prioritize fine particles in the “Preon Solver” (only relevant for CPS).
• Fixed the possibility for artifacts to occur when rendering fluids with CPS using the “Preon Renderer”.

PreonPy:

• Fixed the return value of get_property_type for unit, time and path properties.

[5.2.4] - 2022-09-26

Fixed

• Fixed a synchronization issue when using the “Solid Volume Solver” in combination with MPI and CPS.
• Fixed a potential crash when having a point cloud resource connected to a solid object with dynamic sampling enabled and re-importing the resource using the respective right-click action of the point cloud resource or when using undo/redo.
• Fixed a rare issue causing the “Vehicle Simulation Model” to throw an error on trying to resume a simulation.
• Fixed an issue that sometimes too many solid particles were generated when using CPS.
• Fixed an issue that the number of solid particles was sometimes underreported in the scene statistics when using CPS.
• Fixed a potential crash in the Scene Inspector after an object deletion.
• Fixed the issue that the “Preon Solver” printed error messages by mistake when using temperature-dependent density and MPI.

[5.2.3] - 2022-08-11

Added

• It’s now possible to simulate vehicles featuring different wheel tracks with the “Vehicle Simulation Model”.
• Added missing PreonPy API Documentation for the “Pathlines” object.

Changed

• The option adjust interface bulk modulus is now not disabled by default. Our recommendation is to use it in scenes where you experience “Stuck Particles” deletion.

Fixed

• Fixed an issue with CPS where an “Area Source” connected to an “Outflow Domain” via the connection “Flow Rate” would underestimate the emitted volume.
• Fixed a possible crash when adding loop keyframes to the simulation frame rate or view frame rate property of the “Scene” object.
• Fixed an issue in the automatic connection of a fifth clipping plane to a camera.
• Fixed a crash that could happen in the PreonLab GUI when using density coloring together with enabled closed domain density correction.
• Fixed an issue where the “Deleted particles visualizer” sometimes didn’t show particles that exceeded the high pressure threshold.
• Fixed a crash when adaptive sampling is turned on and the particle size was changed to be uniform across all solvers.
• Fixed possible leakage when using the old multi-solver based fluid refinement system.
• Fixed an issue where applying the right-click action Regenerate volume would not extract the new value for computing the volumetric power given the amount of Watts.
• Fixed experimental mode being enabled by default. This is a regression which was introduced in version 5.2.2.
• Fixed inaccurate “Force Sensor” pressure values and incorrect “RBPS” simulation results of a “Preon Solver” when the property gradient correction was turned on.
• Fixed a bug that the unit of timings could not be set to “seconds”.
• Fixed crash when using the rigid body solver in combination with adaptive fluid resolution and a solid with disabled dynamic sampling.

[5.2.2] - 2022-07-08

Fixed

• Fixed an issue in PreonNode where a “Solid Volume Solver” would only receive the generated particles of one of multiple connected “Solid Volume Sources”.
• Fixed an issue in the “Particle tracker” where the line geometry would be visualized at an incorrect position in the “Preon renderer”.
• Fixed an issue in the pathlines export to CSV files where the positions of the line geometry were saved in the local space of the pathline object.
• Fixed a possible crash when deleting a “Thermal Sensor” that was connected to a “Sensor Plane”.
• Fixed a precision issue that the “Cylindrical Domain” didn’t work correctly at very small scales.
• Fixed an issue that particles were sometimes not refined correctly when using multiple nested refinement domains.
• Fixed a visual artifact in the coloring of solids in case dynamic sampling was enabled and a sensor connected.
• Fixed a possible crash when using the “Force Sensor” and non-uniform fluid particle sizes.
• Fixed an issue that it was possible to use higher ratios from max. to min. particle size than 8 in non-experimental mode. Higher ratios are still possible but are considered experimental.
• The property particle size is now exposed for the “Solid volume source”.

[5.2.1] - 2022-06-27

Fixed

• Fixed a crash while rendering when the sdf method of “Preon Renderer” was set to ZB_DensityCorrected.
• Fixed an issue when the rendered particles target in the User Preferences was exceeded and when using continuous particle size.
• Improved the performance of the coarsening algorithm when using CPS.
• Fixed an issue in the “Vehicle Simulation Model” related to the start frame property.
• Optimized the order in which the geometrical setup of a VSM scene is verified.
• Fixed that the property max. new density error was shown although Time Stepping->adaptive was set to off.
• Fixed a crash when trying to manage presets on the Scene object.

[5.2.0] - 2022-06-09

Added

PreonSolver:

• Added the option continuous particle size that enables per-particle sizes. This allows to use per-particle sizes within a single solver object and replaces the old multi-object approach. It also supports a higher ratio between particle sizes and continuous coarsening. If this property is enabled, the new property min. particle size sets the minimal allowed particle size of the solver while max. particle size sets the maximum. A specific particle size can be enforced in regions of the simulation using a domain object.
• Added the option adjust interface bulk modulus allowing the usage of physical values for phases. It also decreases particle deletion and improves refinement performance. This is only relevant when using implicit equation of state.
• Added the property contact angle for solids to the cohesion model CSS.
• Added the option pressure guided timestep which adjusts the timestep in very dynamic scenes not only based on the predicted velocity field but also taking the pressure Poisson equation into account. This can reduce particle deletion. The new property max. new density error regulates the newly incoming density error allowed before the solve. The timestep this criterion determines is logged as a statistic Time Step: Dynamic Limit.
• Added a statistic Time Step: Explicit Viscosity that now shows a separate statistic for the time step that is determined when the property Viscosity -> implicit is turned off.
• Added the property prioritize fine particles to Pressure Solver->Density Invariant Solver. This is only relevant when using continuous particle size and gives a higher weight to finer particles when computing the average density error guiding the abort criterion. This can improve the simulation quality in scenes with a high ratio between min. particle size and max. particle size.
• Added a coloring option that allows to color particles according to their size.

Domains:

• Added the action type refine_continuous that should be used in combination with a solver with enabled continuous particle size. If this is chosen, the new property target particle size can be used to select a particle size within the domain region.

Sensors:

• Sensor plane and Sensor mesh: Added the ability to connect “Solid Volume Solvers” in order to measure the temperature values of their particles.
• Resulting forces of the cohesion model named CSS on rigids are now also displayed in the “Force Sensor” under the category Adhesion.

GUI:

• In the Plot Dialog, added the option to export statistics to our internal binary format. Previously, only CSV export was supported.
• In the statistics tree of the Plot Dialog, it is now possible to change the unit of all statistics in a group at once.
• Added drag-and-drop support for statistics and CSV files to directly import these files as Statistic Resource objects.
• It is now possible to define custom presets for each type of object.

PreonPy:

• Added triangle mesh access for rigid type objects.
• Added support for Python 3.10.
• Added object.statistics that returns a list of statistics provided in the newer preonpy.Statistic interface.
• Added statistic.name, statistic.quantity_name and statistic.reduction_type which return the full name, the quantity name, and the reduction type abbreviation of a given statistic, respectively.
• The Scene.import_mesh method now supports importing STEP files. The method extends the list of arguments giving you access to set the linear and angular deflection tessellation parameters.
• Added Scene.get_files for retrieving all existing files that belong to the scene.

Miscellaneous:

• Added the new object type “Vehicle Simulation Model” which realizes a co-simulation with AVL VSM™ for an improved car suspension modeling, all-new virtual driving and track interaction.
• Added the new object type “Heat Field” which allows to add or remove heat to or from thermally enabled particles located in a specified volume. Connect it with a point cloud resource for the ability to apply a non-uniform power distribution.
• Added support for the STEP file format. On import, the STEP file is tessellated before being loaded into PreonLab. For guiding the tessellation algorithm, we provide two parameters: linear deflection and angular deflection. The mesh resource now contains two read-only properties number of triangles and number of vertices. This way, you can do a rough inspection of the tessellated STEP geometry. Be aware that the STEP import is an expensive operation and import times would be magnitudes larger than importing a mesh from the currently used formats such as OBJ, PLY and STL. If you want to re-tessellate an already imported STEP mesh resource, you could do that by right-clicking the mesh resource in question and clicking the “Re-tessellate” menu item. It would let you enter different values for the linear and angular deflections.
• Added a PRMESH file format (with the .prmesh extension). This is a binary file format for storing mesh data. The format offers faster loading times (compared to the conventional mesh file formats) due to its data layout specifically tailored for PreonLab as well as a small file size due to its binary representation and the use of compression. You can convert a mesh file on import to the PRMESH file format using the new Convert to 'prmesh' checkbox in the mesh import dialog, or convert already imported mesh resource objects via a right-click action. Note that you can only convert meshes that have a resource object connected to them.
• Added the property rank to the “Air Flow” object. Particles located within multiple air flow fields will only experience the drag forces of fields with the highest rank.
• PreonLab now prints CPU info on Linux systems at program start.
• In the “Point Cloud Resource”, enable aabb from sample points if you want a tight-fitting axis-aligned bounding box without support radius around your sample points. This option is also available in tensor fields (e.g. “Acceleration Field” or “Air Flow”) if the velocity storage implementation is set Gridless.
• Added mode and version fields in the status file (--statusFile). The mode field can be of value postprocess or simulate, depending on which type of run was invoked. version will have the value 1.1 and will update with future changes to this file.

Changed

Preon Solver:

• Renamed the property spacing to particle size.
• Changed the default maximum timestep, increasing it for low particle sizes and decreasing it for higher particle sizes. This improves performance for small-scale scenes and improves stability for large-scale scenes. When using continuous particle size, setting adapt max timestep to particle size lowers the maximum timestep dynamically according to the actual smallest existing particle in the simulation.
• The property temp. based density is now experimental. It utilizes continuous particle size and achieves more accurate simulation results compared to previous versions.
• The cohesion model named CSS is not marked as experimental anymore.

GUI:

• The number of clipping planes is now limited to five per camera. Previously, warnings have been thrown if the user added more than five clipping planes to the scene.
• The Recent Scenes menu now displays the last 10 used scenes instead of 5.
• In the Plot Dialog, the objects in the statistics list are now sorted by their names. Furthermore, statistics for vector quantities form a group now.
• Improved the look and feel of the plot axis in the Plot Dialog.
• When changing to or from a GPU license while a scene is open, you will now be prompted to close the scene first.

Miscellaneous:

• Dynamic sampling can now be enabled for solids in combination with thermal boundary conditions.
• Temperatures defined in particle sources are now assigned to created particles even when thermodynamics is enabled only later during the simulation via keyframing.
• The unit for performance timings can now be set independently of the unit used for time quantities.
• The average conductivity property of thermodynamics solvers has been renamed to conductivity mean, providing the two options Arithmetic and Harmonic. The first option corresponds to the previous On value and the second option to the previous Off value.
• The condition type deleteSolidVolumeParticles has been added to domains which delete particles of a “Solid Volume Solver”.
• The “Thermal sensor” now only shows statistics that are relevant for the current tracking mode.
• It is now possible to open a scene in PreonLab with a “Mesh resource” object that references a broken or corrupted mesh file. An error message will be shown. On PreonNode invocations or when calling PreonCLI with a scene file, it will fail on start.
• The quantity type property of a “Point cloud resource” cannot be changed anymore as soon as its outgoing Field slot is connected to an ingoing Tensor field slot of another object.
• Volume sensor: If a solid mesh is connected, the resulting bounding volume is now shown fully opaque together with the bounding box line geometry of the volume sensor.
• Volume sensor: Changed the default size of 1.0m to 0.02m in the bounding volume generation in case a solid mesh is connected to a volume sensor before a solver is connected.
• The color chosen for statistics is now saved to the .prscene file instead of the .stats file. With this change, the color is preserved when clearing the simulation data and when transferring the scene file.

PreonPy:

• preonpy.Statistic.display_unit, preonpy.Statistic.base_unit and preonpy.Statistic.internal_unit raised an IndexError exception in case the underlying statistic did not exist. This is now changed to raise a preonpy.StatisticNotAvailable exception to be consistent with the other methods provided by the Statistic class.
• Added a preonpy.show_progress attribute which is enabled per default. When enabled, it prints a status log per frame for long-running tasks such as simulate, post_process or exporting a CSV file. The behaviour substitutes the previously shown progress bar for the long-running tasks, which required the progressbar2 package. This requirement is not needed anymore. Previously, the non-existence of the progressbar2 package disabled logging which is not true anymore. The preonpy.show_progress attribute should be used instead of preonpy.show_progressbar attribute, which is deprecated and will be removed in future versions.
• preonpy.Scene.import_mesh raises an InvalidFileError exception, when the import has failed.

PreonNode:

• Removed the option particleBasedLoadBalancing since particle-based load balancing is now the default. Furthermore, the guiding particle-count-based metric was optimized to predict the computational effort more accurately.
• Added the option timingBasedLoadBalancing which enables the timings-based load balancer in previous PreonLab versions. This is now only recommended when using MPI nodes that vary in computation speed.

Optimized

• Preon Solver: Improved the performance when using the Quality cohesion mode by up to 15%.
• PreonPy: Improved the property access performance.
• Plot Dialog: Improved the startup time of the dialog when many objects are selected.
• Improved the MPI load balancer splitting strategy for scenes with sparsely distributed fluid particles.
• Mesh import: Improved the import time for files containing multiple sub-meshes with the single mesh option disabled.

Fixed

Preon Solver:

• Fixed the issue that setting the maximum timestep to the default value did not work correctly for custom particle sizes.
• Fixed the issue that temperature-based quantities did not get updated when loading a scene without simulating it.

Sensors:

• Fixed the issue that “Pathlines” didn’t track refined or coarsened particles correctly. This fix is only available when using the new continuous particle size feature.
• Fixed the issue that the “Thermal sensor” would yield wrong values in post-processing mode when solids overlapped each other.

GUI:

• The right-click action for setting a transform key is now also offered for the euler angles property. Previously, it had only been available for the position and scale properties.
• Fixed the issue that the “Remove key” right-click action in the property editor had not been offered for certain properties although they had a keyframe set.
• Fixed a crash in the Plot Dialog when clicking on an object that does not contain any statistics at all.
• Fixed the issue that when exporting statistics from the Plot Dialog, the header of the exported CSV file did not show the correct unit(s) if it had been manually changed before.
• Buffer names visible to the user, e.g., via particle picking, particle tracking or export of particle data now follow the naming conventions of the statistics.

Rigid body solver:

• Fixed an issue that occurred when using two-way coupling, refinement and continuous particle size.
• Fixed inaccurate “Potential Energy” statistics for dynamic rigid bodies.

Preon Renderer:

• Fixed an issue that exclusive-range rendering did not work when rendering single particles with “Preon Renderer”.
• Fixes an issue that objects didn’t update correctly when using a higher view frame rate than simulation frame rate.

Miscellaneous:

• Fixed a crash when duplicating an “Open boundary plane” with CTRL + D.
• Fixed an issue where the “Open boundary plane” could miss the latest state of the “Preon Solver”.
• Fixed an issue that occurred if loop keyframes have been employed in the simulation frame rate or view frame rate property of the “Scene” object.
• Fixed an issue where domains set to deleteFluidParticles would also delete particles of a “Solid Volume Solver”.
• Removed an error message with respect to QBasicTimer shown in the error log when closing the Plot Dialog, and fixed the potential problems it would have caused.
• Fixed the issue that area source backplane could influence rigid body simulations.
• Fixed an issue when using crop-left operations on “Solid Volume Solver” objects.
• Fixed the issue in the “Solid Volume Solver” that an optimization reducing the required disk space was not applied in MPI simulations.
• Fixed the formatting of the license table which is printed when calling PreonCLI or PreonNode with --licenseList.

PreonNode:

• Fixed a simulation quality issue when using MPI and the Herschel-Bulkley viscosity model.
• Fixed an issue where cumulative statistics would start off with an outdated statistic.

PreonPy:

• Fixed the issue that delete_object would not clean up the memory of deleted objects correctly.

[5.1.4] - 2022-02-07

Fixed

• Fixed a crash that occurred on applying a deletion domain to a porous rigid and the deletion having its domain defined by a solid connected via the TriangleMesh connection slot.
• Fixed a crash in the Plot Dialog when accidentally trying to set the color for a non-statistic tree item.
• Fixed stability issue when using Periodic Boundary Conditions and MPI.

[5.1.3] - 2022-01-19

Fixed

• Fixed a possible PreonNode crash on startup when using MPICH on Linux.
• Fixed a potential (and rare) crash when using local refinement and MPI.
• Fixed a rare crash when using solvers with different spacings (but no refinement) and MPI.
• Fixed a potential MPI timeout when using closed domain correction in the “Preon Solver”.
• Fixes an issue in the video export dialog that OpenGL view frames could not be assembled into a video anymore.
• Fixed an issue where the “Export sample data to CSV file” action would not work correctly for some sensors with individual frame rate enabled.
• Fixed a crash when using periodic boundary conditions and gradient correction.

[5.1.2] - 2021-11-30

Fixed

• Improved accuracy of flow rate and summed volume measurements when using adaptive resolution for the sensor plane and sensor mesh.
• Fixed an issue in the Keyframe Editor where adding new keyframes via double-clicking the mouse would also update the value range of the graph view instantly.

[5.1.1] - 2021-11-12

Fixed

• Fixed a crash in the Keyframe Editor that occurred on using CTRL + Z to undo the generation of a keyframe.
• Fixed that the adhesion property of solids was hidden in the Property Editor when no “Preon Solver” was present.
• Fixed issue that preonmpiadapter.sh failed to compile on IBM Platform MPI.
• Fixed issue that “Preon renderer” did not render solver objects belonging to the same refined fluid as one when post-processing.
• Fixed a bug that occurred when using looped keyframes in position control modes velocity and acceleration and revolutions_PerSecond in the orientation control mode.
• Fixed an issue that differing spacings were also allowed for snow solvers.
• Fixed issue that during post-processing, the velocity of position-keyframed objects in some occasions could have been different to the one used during the simulation when having adaptive timestepping.

[5.1.0] - 2021-11-08

Added

Preon Solver:

• Added the experimental cohesion model CSS which uses a Continuum Surface Stress (CSS) formulation. For now, it supports exactly two phases and boundary.
• Added experimental “Void Solver” that can be used to model a force that pulls fluid particles into voids.
• Added right-click action “Create periodic boundary conditions” that inserts a “Periodic boundary solver” and two “Periodic boundary planes”, and sets up all the required connections.

Snow solver:

• Added a Jacobi preconditioner which decreases computation time by up to 5 and improves stability. The preconditioner is enabled by default and can be toggled off via the property use preconditioner.

Solid Volume Solver:

• The solid volume solver now supports adaptive resolution.

Sources:

• Particles emitted by an Area or Volume source can now be initialized with a temperature distribution by connecting a “Point cloud resource” via the TensorField slot.
• The Area source now supports user-defined velocity profiles provided by a “Point cloud resource”
• Added predefined pipeflow velocity profile for the Area source.

GUI:

• The Scene object now allows defining the default units to be used for the statistics and physical quantities of all objects in the scene. The default units for new scenes can be set in the user preferences.
• The list of properties in the Property Editor can now be filtered to quickly find properties by name, by value or by unit.
• All solvers now support the right-click action “Export state to CSV file” (e.g. the “Solid Volume Solver”, too).

Sensors:

• Thermal sensor: On sample data export or PreonPy buffer access, thermal quantities can be added from connected “Point cloud resource” objects in areas where no thermal interaction took place (i.e. “dry” areas).

Plot Dialog:

• Added the possibility to jump to the corresponding frame when clicking on the plot by activating the “Update time on click” option.
• Added an option, “Group by statistic instead of object”, for alternative representation of the statistics tree where the statistics are first grouped by name and afterwards by object.
• In the statistics list, selecting a node now also selects all of its descendants. Moreover, deselecting a node also deselects all descendants.
• In the statistics list, nodes are now shown as selected if at least on of its children is selected.
• Filtering the statistics list now also considers names of the ancestor nodes in the tree.
• Changing the units of statistics is now persistent between openings of the same scene. When the selected unit for a statistic diverges from the scene’s default unit for the respective type of quantity, the unit is serialized to the scene file.
• The list of statistics available for an object is now visible before starting the simulation.

PreonPy

• Added object.statistic_buffers() for fast statistics access.
• Added object.associated_scene() for convenient access to the underlying scene.
• Added object.is_property_writable() to test if a property is writeable.
• Added preonlab.selection() for accessing the list of objects that is are currently selected in PreonLab. Because it relates to the UI, this is only available in the PreonLab Console.
• Added global_transform() for accessing the global transformation matrix of an object. It can be used on preonpy.Rigid and preonpy.SensorPlane objects.
• Restructured PreonPy API documentation such that it contains less duplicated parts.
• Added object.particle_buffers_list for Solvers and Solids. It will return multiple buffersets for preonpy.Rigid with dynamic sampling turned on. In all other cases, it will return a list with just one element.
• Added get_line_data for preonpy.Pathlines that provides buffer access to pathline data.
• Added preonpy.Quantity as a utility type holding a value together with a unit and providing unit conversion.
• Added preonpy.Statistic as interface for querying a statistic. It will return results as preonpy.Quantity instead of plain values. It can be obtained by calling object.statistic("statistic_name").
• Added preonpy.get_property("property_name") for getting property values as preonpy.Quantity.
• Added the possibility to set properties with quantities or tuples (e.g. solver["spacing"] = 5, "mm").
• It is now possible to pass preonpy.Quantity objects of type time to a lot of methods like e.g. Scene.simulate.

Miscellaneous:

• Added the support to reserve certain amount of licenses for machines or users through RLM’s RESERVE option.
• Thermo solver: Added the convergence criterion property that allows switching between different formulations of the time step estimation.
• Point cloud resource: Added the ability to import a heat flux distribution and map it to a solid’s surface as the thermal boundary condition.
• Added a --statusFile option to PreonNode and PreonCLI for passing a file in which the current status and progress of a simulation or postprocessing run is written.
• Added the option to enable an individual frame rate for solvers. This allows serializing data with a different simulation frame rate than defined in the scene object.
• Added the option to enable an individual frame rate for “Preon renderer” objects. This allows creating images with a different view frame rate than defined in the “Scene” object.
• Added the option to enable an individual frame rate in a sensor. This allows to update/export a sensor with a different view frame rate than defined in the “Scene” object.
• Added right-click actions “Create refinement solver (level 1)” and “Create refinement solver (level 2)” to all solvers that support refinement.
• Added surface proximity fill type to volume generating objects like the Volume Source or the Box Domain. The primary application of this is to refine inside a narrow band around a geometry surface.
• Added support for cancelling a simulation/post-processing run using an abort file. During a simulation or post-processing, if a file named ABORT.txt is placed in the simulation’s working directory, the run will be aborted after the end of the current frame and the placed abort file will automatically be removed.
• Added a new download format for PreonNode which comes bundled with OpenMPI.
• Added a new download format which contains all Preon binaries for both, Windows and Linux. It does not contain an installer but can simply be unzipped.
• Added logging of scene statistics (the ones shown in the OSD) of a simulation for PreonNode and PreonCLI. We log these statistics at each frame, and the logging is turned on per default and could be switched off using the --no-progress CLI option. Using the --logProgressEveryNthFrame one could log only at every n frames.
• Added the option automate cell size to the “Sensor plane” which synchronizes the cell size with the lowest connected solver spacing at all times.

Changed

Preon Solver:

• Improved pressure solver stability when using adaptive resolution.
• Blocks of refined particles are now rotated according to the velocity of the original coarser particle, which reduced grid-like patterns.
• Added property refine to transition level threshold that controls when very coarse particles are refined due to neighboring very fine particles.
• The properties max high density particles and high density threshold are available again when using adaptive resolution.
• Slightly tweaked cohesion, viscosity and thermodynamics models when using adaptive resolution.
• It is now possible to use different spacings for different solvers. Spacings are not synchronized automatically anymore.
• Improved the model for wall functions. In addition, the y+ value is now capped to 300 which is the generally accepted validity range in the literature. Previous y+ calculations would allow arbitrarily large values of y+ beyond the validity range.

Solid Volume Solver:

• The OSD with sim statistics is now shown per default.
• Changed the default_coloring to the palette of rgb_coloring and removed the latter.
• Changed the default coloring mode from velocity to temperature.
• Removed the property groups Deletion Criteria and Density computation from this object type.
• Removed coloring options that were undefined for this object type.
• Removed the right-click actions “Create refinement domain (level 1)” and “Create refinement domain (level 2)” from this object type.

GUI:

• Scene Inspector: Pressing the icon beside the name of an object toggles its visibility.
• Scene Inspector: The names of the object groups are now considered when searching for objects via the Scene Inspector.
• Postprocessing dialog: Renderers are only listed as objects to post-process if at least one camera is connected.
• Changed the naming of the coloring option temperature for a solid to boundary type. Depending on the thermal boundary condition, it will color according to a constant temperature or constant heat flux. This coloring option is not available if the boundary type is set to None.
• In the Plot Dialog, min/max/avg statistics for the same quantity are now grouped together.
• Added right-click action “Copy PreonPy name” for statistics in the Plot Dialog. It has the same functionality as the corresponding action in the Property Editor.

Sensors:

• The “Pathlines” sensor now supports tracking particles that have been refined or coarsened. Please note that this is not possible for old simulation data created with PreonLab 5.0 or older.
• In the “Thermal sensor”, the OSD label for time-averaged quantities was changed from Agv. <quantity> to Time-avg. <quantity>.
• Deleted particles visualizer: Renamed statistic names Cum. deleted particles to Cum. Deleted Particles, Cum. High pressure to Cum. Deleted High Pressure Particles, Cum. Stuck to Cum. Deleted Stuck Particles and Cum. CFL violation to Cum. Deleted CFL Violating Particles.

Domains:

• Periodic boundaries can now be used with adaptive resolution.
• “Outflow domains” now reach the target flow rate more reliably. The “Outflow domain” object has been changed to be an experimental feature. The manual before referred to it as a prototype.

Miscellaneous:

• Fixed an issue that could occur if the behavior of a solid was set to cache and keyframes were defined regarding the transformation of the solid.
• Tensor Field import dialog: The dialog now asks for the unit of the respective physical quantity to be imported (e.g. of velocity) and not only for the distance part of it.
• Point cloud resource: Added the property quantity type that specifies the physical quantity that is imported via the resource. Based on this type, the outgoing TensorField slot name is changed to indicate what the resource is able to provide, e.g. VelocityField.
• The connection types VelocityFieldand TemperatureSamples have been replaced by the more general type TensorField.
• The tensor data import from Ensight Gold files is not aborted if a time set number is provided in the .case file for non-transient geometry or variable files, but simply ignored.
• All properties holding a unit now represent the unit by its abbreviation (e.g., mm). Previously, some properties used the full unit name (e.g, Millimeter).
• Removed support for the length units Decimeter and Inch, as well as for the temperature unit Fahrenheit.
• Improved the visualization of the “Periodic boundary plane” by switching to a coordinate-axis like representation to make it easier to position it correctly.
• The “Periodic boundary solver” and the respective “Periodic boundary plane” are not marked as experimental anymore.
• The “Y+ sensor” and all properties in the property group Wall Function of the fluid solvers and solid objects are not marked as experimental anymore.
• Opening scenes with old simulation data, where statistics do not contain unit information, will cause an error, and subsequently not load the affected statistics. This applies to statistic files generated with PreonLab prior to v3.2.
• For the “Periodic boundary solver”, the properties of group Appearance are now visible in the Property Editor.
• On adding a “Solid Volume Source”, no default connections are drawn to existing meshes anymore.
• The default value for the property automatic resize of a “Solid Volume Source” has been changed to Off.
• When specifying invalid licensing options, PreonNode and PreonCLI will now quit with return value of 1 instead of using the default licensing policy.
• Removed the live update of the value of a property in the Property Editor while one of its keys is dragged in the Keyframe Editor.
• Removed the wireframe option from property render mode for all particle solvers.
• Renamed the coloring mode none to uniform.

PreonPy:

• Disabled properties cannot be accessed anymore.
• If particle_buffers was called on a solid with dynamic sampling turned on, a RuntimeError was raised. Now a preonpy.SubsamplingError is raised instead.
• Added get_property_grouping for querying the grouping used in PreonLab’s Property Editor from PreonPy.
• All properties and method arguments representing a unit now expect the unit to be given in its abbreviation form (e.g, mm). Previously, some properties and methods expected the unit to be represented by its full name (e.g., Millimeter).

Optimized:

Preon Solver:

• Improved performance when using adaptive resolution by up to 20%.

Fixed

Solvers:

• Fixed a rare issue that refined fluid particles could leak through geometries when pausing and resuming a simulation.

Preon Solver:

• Fixed a crash that could occur when pausing the simulation, inserting a refinement domain and resuming the simulation.
• Fixed crash when using very small spacings (less than 4e-06) and adaptive resolution.

Thermo Solver:

• Fixed an issue that occurred when a solid’s boundary type was set to heat flux and Thermodynamics->implicit was enabled in a solver.

GUI:

• Generating multiple pathlines shows only one frame range dialog box, whereas previously it appeared for each of the selected “Pathlines” objects.
• Fixed an issue in the Property Editor that when pressing certain keys on the keyboard, the column value could disappear.
• Fixed an issue in the Keyframe Editor that the tooltip showing the current value did not vanish after closing the dialog.
• Fixed an issue where the properties in group Thermo Solver would not be forwarded to the implicit thermodynamics solver.
• The OSD of a mesh-based sensor will not display a color legend or any stats as soon as one removes the TriangleMesh connection to the solid or the Particles connection to the solver(s) anymore.
• Fixed an issue that some scene properties had been marked as modified when opening a scene, although their value corresponded to their default value.
• Fixed an issue when clicking on the “Show curve” right-click action in the Property Editor for properties that consist of multiple parts (e.g. position).

Sensors:

• Fixed that the “Volume Sensor” would show the 3D volume of a 2D solver when the property sub particle precision was activated.
• Deleted particles visualizer: Fixed mismatch between simulation and playback.

Miscellaneous:

• Added unit to statistics of particle deletion domains.
• When executing scripts via the PreonCLI or the PreonLab Console, the exit() function will behave similarly to the Python interpreter and will not raise an error.
• If more than one “Solid volume source” is connected to a “Solid Volume Solver”, the generated particles of both sources are now added to the solver.
• Fixed an issue where changing the constant temperature for the boundary type temperature in a solid would not be considered in a simulation run after saving and reloading.
• Fixed an issue in the “Periodic boundary solver” that for overlapping boundary planes, only one boundary particle has been generated in total instead of one for each plane.
• Fixed an issue where a “Periodic boundary solver” would use adhesion when it should have used cohesion instead.
• Sources are now automatically connected to the only “Preon Solver” in the scene even if there is an additional “Periodic boundary solver”. Previously, the existence of the other solver prevented the connections to be drawn automatically.
• Fixed an issue where fluid leakage could occur in scenes containing a fluid solver with multiple refinement levels, solids with dynamic sampling enabled and adaptive sampling disabled, and extended per-particle solid data (e.g. via a defined thermal boundary condition or via a sensor which collects per-particle data like max pressure in the force sensor).
• Fixed an issue in the CSV import of keyframes for properties with identical names that are only differentiated by their property group name (e.g. Front::nonlinear spring force).
• Fixed a bug that the “Particle tracker” did not show the trajectory of the particle anymore.
• Fixed a bug in the Keyframe Editor that for some properties, keyframes could not be moved via mouse dragging.
• Keyframe Editor: “Update time on click” can be used while having a property with locked keyframes selected.
• Fixed a bug that the “Point cloud resource” did not apply the offset set by the user in the import dialog.
• Fixed crash when picking a rigid particle and then triggering a rigid resampling (for instance by changing the thermodynamics boundary type).

[5.0.4] - 2021-08-31

Fixed

• Fixed an issue when using refinement and temperature-dependent viscosity or temperature-dependent density.
• The “Thermal sensor” will only measure the conjugate heat transfer if the following preconditions are fulfilled: a) it is connected to a solid with thermal boundary tpye set to None b) a “Solid Volume Solver” and a thermally enabled fluid solver are connected to the “Particles” slot of the sensor.
• Fixed a crash in the “Thermal sensor” where the conjugate heat transfer would be computed between a “Solid Volume Solver” and a fluid solver, but thermodynamics was not enabled in the fluid solver.
• Fixed a bug in the “Solid Volume Solver” that prevented the temperature buffer to be written to disk with lossless compression.
• Fixed an issue in the “Thermal sensor” when using refinement and fluid particles with coarser spacings are observed by the sensor.
• Fixed an issue that the min and max pressure statistic of the “Preon Solver” could be incorrect when using MPI.
• The number of particles statistic in the scene is now available at substeps when using MPI.
• Fixed a crash that occurred when connecting a “Solid volume solver” to a “Y+ sensor” via the Particles slot.

[5.0.3] - 2021-07-23

Fixed

• Renamed the property Pressure Solver->Density Invariant Solver->density error back to its intended name. It had wrongly been renamed to Density Error.
• Added the option “disableThreadBinding” to PreonLab, PreonCLI and PreonNode which disables automatic thread binding.
• Added “New Y+ Sensor” to right-click action “Connect Sensor” of rigids.
• Fixed an issue where the total heat content of a solume volume solver would be incorrectly shown to be zero in specific cases.
• Fixed an issue in the force sensor statistics in cases where the following is used: momentum wall function; Herschel-Bulkley viscosity model; temperature-based viscosity.
• Fixed an MPI timeout in cases where the property script nearby particles of the area source is active.
• Fixed a possible MPI timeout during scene loading.
• Fixed an issue that calling the PreonPy method Scene.import_mesh with a relative path leaves the property pointing to the respective file with the path relative to the working directory. Now, an absolute path, or a path relative to the scene directory in case the file is inside the scene directory, is used.

[5.0.2] - 2021-05-27

Fixed

• Fixed a crash in the Keyframe Editor when toggling “Update time on click” and no property was selected.
• Fixed an issue that the timeline could update to an incorrect frame using the “Update time on click” feature in the Keyframe Editor if the view frame rate differed from the simulation frame rate.
• Fixed vendor-specific crash when starting PreonLab on a GPU from AMD.
• Fixed an issue that it was possible to insert a Periodic Boundary Solver into a scene that already contains a Snow Solver.
• Fixed an issue with the automatic resize of the “Solid Volume Source” in cases where an “Area Source” was present.
• Fixed a crash when switching the property behavior of a solver mid-simulation.
• Fixed issue that it was possible to connect multiple “Preon Solvers” to a “Periodic Boundary Solver”.
• Fixed issue that fluid leakage could occur in scenes that contain some solids with adaptive sampling enabled and others with adaptive sampling disabled.
• Fixed a “Solid Volume Solver” initialization issue.
• Fixed a link in the About dialog.
• Fixed a crash when a “Y+ sensor” was connected to a rigid in a scene without a solver.

[5.0.1] - 2021-05-14

Fixed

• Fixed a bug that cumulative timing statistics of the scene had been reset when resuming a simulation.
• Disabling show osd in the Scene UI Settings now also disables the OSD in the video output again.
• Fixed a bug that horizontal scrollbars where unreactive if the scrollable content was only marginally larger than the scroll area.

[5.0.0] - 2021-05-03

Added

Preon solver:

• It is now possible to use three particle levels (instead of just two). Three levels are only supported in combination with the new Continuous correction method.
• The option sampling correction method determines how the solver deals with artificial density errors, usually introduced by refinement, coarsening or initialization. Continuous is always used for adaptive simulations and will correct these errors over multiple time steps. Instant is the default for uniform simulations and is equal to the behavior in 4.3.3.
• Enabling the option optimize for closed domain can improve the quality of simulations in fully filled, closed domains.
• The option closed domain density correction slightly adjusts particle densities to ensure a fully filled domain. This option is only available if optimize for closed domain is enabled.
• Added experimental thermal and momentum wall functions. They use the “Law of Wall” to correct the heat flux and shear force in a coarsely resolved scene, respectively.
• Reduced the number of pressure solver iterations by up to 30%. Turning off the improved RJ property reverts to the behavior in 4.3.3.
• Added the Adaptive Resampling properties steps between simplifications, merge max. vel deviation and merge max. relative vel deviation that specify when particles can be merged in an adaptive simulation.
• Added average pressure statistic.
• Added presets for air and oil (with code “5W30”).

Snow solver:

• Added a so-called “greedy initial guess system” which needs fewer iterations for comparable accuracy. The warm start option was removed in favor of this automated system.

Solid volume solver:

• Added an experimental “Solid Volume Solver”. It computes thermal quantities on particles representing the volume of a solid and can be used for conjugate heat transfer computations.

Sources:

• Added an experimental “Solid Volume Source” which must be used to generate particles for the experimental solid volume solver.
• Added the option correct area discretization to the area source that slightly increases the outflow velocity to counter the discretization error of the area.
• Added the option script nearby particles to the area source that can help to stabilize the outflow of the source for continuous emission.

Domains:

• Replaced the refine condition type with the types refine_level1 and refine_level2 specifying the desired refinement level.
• Added the experimental “Periodic boundary solver” and “Periodic boundary plane”, which allow to add periodic boundary conditions to the simulation.

Solids:

• Added the boundary type heat flux to the thermodynamics properties. If set, the user can provide a constant heat flux as the boundary condition.
• Added a right-click action “Connect Sensor” which allows to connect rigids to new or existing sensors of the following types: “Force sensor”, “Thermal sensor”, “Height sensor”, “Wetting sensor” and “Sensor mesh”.
• Added the option adaptive sampling that enables or disables the potential usage of adaptive sampling when using a fluid with multiple refinement levels. This is enabled by default and can improve memory consumption and performance.

Sensors:

• The new sensor “Deleted particles visualizer” renders those particles that were deleted by the solvers to which it is connected to. This allows to detect issues in the simulation setup or solver parameterization.
• Added the experimental “Y+ Sensor” to visualize wall function resolution.
• The “Thermal sensor” (formerly “Heat flux sensor”) now checks for the applied thermal boundary condition on the connected solid object and measures corresponding quantities.
• The “Thermal sensor” can now observe the conjugate heat transfer between a solid volume solver and a fluid solver.
• The “Thermal sensor” accepts the connection of both, liquid solvers (e.g. fluid) as well as solid volume solvers.
• Added the property track surface normal to the “Thermal sensor”. If enabled, surface normals are added to the list of quantities that can be exported.
• Added fluid temperatures to the list of quantities that can be exported from the “Thermal sensor”.
• The name of the “Air Flow Visualizer” has been changed to “Vector Field Visualizer”. It now also works with “Acceleration Fields”. The connection was renamed to “VectorField” accordingly.
• Added the property track max shear stress to the “Force sensor”.
• Added the connection slot “CenterOfRotation” to the “Force sensor”. This slot accepts incoming “Transform” connections. If connected, the sensor will use the global position of the connected object as the center of rotation during torque computations.

GUI:

• Add a new bright color style for the user interface to complement the existing dark mode. The mode can be switched in the user preferences.
• Added a right-click action “Add badpoint” for the “Volume source”.
• Added right-click actions to create “Group” objects, to move objects to existing groups and to remove object from groups.
• Extended the mesh import dialog with options to create a “solid group for each file” or to create “one solid group for all files”.
• In the “License Information” dialog, the labels of available license options are more descriptive now.

Connection Editor:

• The Connection Editor will now by default group objects together if they are part of a “Group” object. This feature can be turned off via the “Autogrouping” checkbox.
• If all objects that are part of the same group are also grouped together in the Connection Editor, the displayed box will contain the name of the “Group” object.
• By default, if a “Group” is selected in the scene inspector, its sub-objects are also shown in the Connection Editor. This behavior can be changed via the “Also grouped objects” checkbox in the Connection Editor.
• Added a “Form group” button to create a group box based on “Group” object assignments.
• Categorized the slot filter section in order to quickly view or hide many slots with one click.

Keyframe Editor:

• Added a right-click action in the properties table to delete all keyframes of the selected keyed and unlocked properties.

Miscellaneous:

• Added initial support for solver plugins.
• Added the Acceleration Field object to the Force Fields object group to allow the user to specify additional accelerations that PreonLab should respect. It supports static and transient data over the new Tensor Field Import.

PreonPy:

• Added support for having multiple scenes opened at the same time.
• Added the close_existing argument to the preonpy.Scene constructor to specify what should happen with currently opened scenes. Also preonpy.multiple_scenes can be used to set the default behavior if close_existing was not passed.
• For a point cloud resource, import_from_csv can be called to read temperatures or velocities from CSV files.
• For rigids, apply_connected_point_cloud can be called to map a temperature field onto its surface particles.
• As a replacement for the current_scene property, the function get_scenes() (and for the PreonLab Console the property preonlab.current_scene) was added.
• When using PreonPy as a Python package (e.g. not inside PreonLab or PreonCLI), it is now possible to select the favored license without first checking out another one.
• Added preonpy.set_log_dir and preonpy.get_log_dir for specifying where log files should be written.
• Added set_default_scene_dir and get_default_scene_dir for specifying where new scenes should be created.
• Added preonpy.Group as a container for groups.
• Added support for Python 3.9.
• Removed support for Python 3.5.
• Air Flow and AccelerationField are now exposed in PreonPy. Added import_from_csv option similar to PointCloudResource.
• Added Type Annotations for better IDE support and better documentation.

PreonNode:

• Added a --continue parameter that allows a previously canceled or otherwise stopped simulation to be continued based on the last written scene statistics.

Tensor Field Import:

• The import structure of tensor fields has been generalized and is accessible through File->Import->Import Tensor Field. Supported are Airflow, Acceleration, Velocity, Temperature. Transient data uses the same import.
• It is now possible to crop imported transient data, i.e., to define a smaller time range than was imported using the Start Time and End Time properties.
• Added the ability to loop (i.e., repeat) the transient data arbitrarily many times by defining a Duration greater than End Time - Start Time.
• Added the ability to Offset the time range that specified by the data to be imported.
• Added a right-click action to airflows and acceleration fields to import data for an existing object.
• Added a user option for transient data to Use Existing Data such that the conversion process to .prtensor can be (partially) skipped if the files are already present.

Changed

Preon solver:

• Removed support for the loading of .prstate files that were created with versions older than PreonLab 1.0
• Refinement is now always restricted to the defined refinement domains. All collider options related to refinement “buffer zones” are removed. This usually significantly reduces the total number of particles.
• Unphysical pressure forces could be significantly reduced in regions where particles of different sizes interact.
• Reduced the effect that fine particles “creep” between coarse particles and boundary in an unphysical way.
• Improved the quality of the cohesion in regions where particles of different sizes interact.
• The simplification algorithm now supports resampling of regions in which fine and coarse particles are mixed. This typically decreases the overall particle count.
• Removed the optimization that scripted particles which are not contributing to the simulation are excluded from internal data structures. As a result, these particles are now visible to sensors. We recommend to use coarser particles sizes in these regions to improve the performance.
• The limit of one thousand keyframes for temperature-based shear viscosity and bulk viscosity as well as density has been removed.
• Thermodynamics is enabled or disabled by using the new toggle property thermodynamics. It replaces the old system type property. If the removed system type isolated is loaded from an old scene, thermodynamics is set to Off in this case.

Snow solver:

• The default tolerance of the “Elastic Solver” has been lowered to 0.001 (previously 0.01).

Sources:

• The Volume source now ignores its z scale for 2D simulations.

Solids:

• Renamed the property system type to boundary type.
• Renamed the property temperature to constant temperature.
• Changed the boundary type ClosedFixed to temperature. The property constant temperature can only be set as a boundary condition if this particular system type is set.

Sensors:

• Changed the name of the Heat flux sensor to Thermal sensor.
• Removed the property physical value from the force sensor. The decision on which physical value to display is now defined by the coloring mode alone.

Rendering:

• The “Preon Renderer” now always uses the Density_Adaptive signed distance field method for fluids with different particle sizes as sdf method. This means that multiple refinement levels are always rendered as one fluid if they have the same material.

GUI:

• The graphical user interface has been refreshed and the usability improved.
• Dialogs follow now the visual style of the main window, with a toolbar on the top and the settings docked to the right.
• In the Plot Dialog and the Keyframe Editor, zoom using the mouse is anchored on the mouse cursor (for wheel and right-click-drag).
• Removed the “Type” column from the scene inspector. The type of an object is now shown in the tooltip.
• The filter in the “Scene Inspector” hides group items (ex: categories) for which all children are filtered out.
• Right-click actions on selected objects will now always be applied to all objects in the selection.
• Changed the category name of solvers from Fluids to Solvers in the scene inspector and in the menu entry “Add”.
• When clicking the “Arrange” icon in the Connection Editor, the positions for all objects that are not visible are cleared.
• The playback/postprocess start and end markers in the timeline are now shown regardless of the chosen mode.
• Replaced the “Windows” menu by a “View” menu that only allows to switch between single view and quad view.

Plot Dialog:

• Statistic names and Plot Dialog settings have been moved to the right of the plot view.
• Statistics are now grouped by objects.
• The Save Image button now displays the object’s name as a title and a legend.
• Added Copy Image button which exports the image to the clipboard (this also works with Ctrl+C).
• Added settings to the user preferences that let you choose between using theme colors or user-defined colors for image export.

Keyframe Editor:

• If a keyframe sequence is locked, the keys are no longer shown in the view of the curve. This improves readability and performance.
• When hovering or clicking on a loop segment, the original key and segment responsible for this part of the looped segment are highlighted/selected. Similar, if a segment is selected that is looped, the looped part is also highlighted.
• Only the selected keyframes instead of all are now copied.
• The unit is now shown in more places in the Keyframe Editor.
• The list of properties can now be filtered to quickly get to the intended property.

Car Suspension Model:

• Renamed the property car body mass to sprung mass.
• Renamed the options for the reference point from axleLoad and uncompressedSpring to compressed state and uncompressed state, respectively.
• Renamed the property mapped unit to mapped.
• Renamed the options for the property mapped from NewtonPerMeter and Newton to Coefficient and Force, respectively.
• Grouped the per-wheel suspension parameters for the wheels at the front axle and rear axle into property groups Front and Rear, respectively. Note the changed PreonPy names.
• Grouped the general properties for nonlinear suspension modeling into the new property groups Nonlinear Springs and Nonlinear Dampers.
• Removed the property parameter input. The per-wheel suspension parameters have to be provided for the wheels at the front axle and the wheels at the rear axle separately.

Miscellaneous:

• Changed statistics names across all object types so that they follow a consistent naming scheme.
• Updated the Alembic library to version 1.7.16 and the OpenEXR library to version 2.5.3.
• It is not necessary or recommended to specify the OMP_PLACES and OMP_PROC_BIND environment variables anymore. PreonNode, PreonPy and PreonLab will automatically set up the thread binding if appropriate.
• Thermodynamics in the air object is enabled or disabled by using the new toggle property thermodynamics. It replaces the old system type property.
• Removed the Bullet plugin from the available Rigid body solvers.
• Improved the error message in case no license could be found at all.

PreonPy:

• By default, existing scenes will not get closed anymore. You can set preonpy.multiple_scenes = False or pass close_existing=True to the preonpy.Scene constructor to get the old behavior again.
• When using PreonPy as a Python package (e.g. not inside PreonLab or PreonCLI), a license is not checked out directly after executing import preonpy anymore.

Optimized

GUI:

• Optimized the “Scene Inspector” filtering performance for scenes with many objects.
• Optimized the performance of the “Keyframe Editor” when displaying large number of keyframes. Among general performance improvements, the single keyframe points will not be displayed if there are more than 25000 keyframes. Furthermore, the curve will not be anti-aliased in this case.

Miscellaneous:

• Improved the performance of particle encoding/saving.
• Improved the performance when using the “Density_Adaptive” method in the Preon Renderer.

Fixed

Snow Solver:

• Impulse Boundary Handling: Fixed an issue where collided particles were not generating elastic forces for their neighbors.

Solvers:

• The total heat content of the particles of a solver is now given with zero Kelvin as the reference point (as opposed to zero degree Celsius before).

Sources:

• The Quality filling mode of the Volume Source now works correctly for 2D.
• Fixed an issue that let fine particles may pass through area sources in adaptive simulations.

Sensors:

• Fixed an issue where wetting sensors could generate data that was out of sync with the associated solid particles and could not be loaded later.

GUI:

• Fixed an issue where the right-click action “Set pivot to mean position” did not create an undo/redo event.
• Fixed an issue where PreonLab would fail silently if no valid GL context could be created. A warning message is now shown.
• Fixed an “Empty filename passed to function” warning that can appear when using file dialogs.
• The OSD is now updated immediately when an object is been renamed.

Plot Dialog:

• The zoom now locks before the plot lines disappear.

Keyframe Editor:

• Fixed the issue that the Keyframe Editor did not update if a property with no keyframes is shown and the property value is changed in the Property Editor.
• Fixed the issue that CTRL-double clicking on an enum while having selected multiple rows changes the other rows even though no change was intended.
• Fixed the issue that the curve after a loop keyframe was always drawn as a linear curve.
• Fixed the issue that inserting invalid x-values in the keyframe table resulted in 0. Instead, no change is applied now.
• Fixed the issue that right-click actions in the properties table did not act on all selected properties.

Miscellaneous:

• Fixed a Preon Renderer issue that shadows casted by fluids sometimes showed visual artifacts.
• The first solver in a scene does not longer need to be active when simulating multiphase simulations.
• Fixed the --logDir parameter for PreonNode.
• Fixed an issue in the CSV export of per-particle sensor data that could lead to negative position values being rounded.
• Fixed the issue that it was possible to create or delete connections during a simulation, which could lead to crashes.

Tensor Field Import:

• If only a subset of the transient data described in the Ensight Gold format is imported into the Air flow object, omitted frames would not be interpreted as missing frames.

Deprecation notices:

• Statistic names across different object types have been harmonized. If you use the old statistic names via PreonPy, you will get a deprecation warning.
• The PreonPy property current_scene will be removed in one of the upcoming releases. Please use get_scenes() and preonlab.current_scene.

[4.3.3] - 2021-01-29

Fixed

• Fixed a bug that the “Scene” object was not editable with the graphical user interface anymore.

[4.3.2] - 2021-01-28

Fixed

• Fixed crash when loading a scene that contains a height sensor connected to a rigid, but no Preon Solver.
• Fixed possible crash caused by the Volume Sensor after inserting a Preon Solver.
• Fixed snow solver fallbacks that were triggered when using a user-specified number of minimum iterations although the solver was below residual.
• Fixed a bug in the transient airflow import in the case where a static geometry is imported and smooth input is enabled.
• Fixed a crash on trying to delete the “Scene” object.
• Fixed a warning that has been printed when trying to rename the “Scene” or “Scene UI Settings” objects.

[4.3.1] - 2020-12-15

Fixed

• Fixed a rare crash in the keyframe editor when switching the order of looped keyframes.
• Improved the performance of keyframe interpolation.
• Fixed an issue where the list of (filtered) statistics in the Plot dialog would not update correctly after renaming or deleting an object.
• Fixed a simulation stability issue that occurred when emitting fine particles from an area source that are simplified near the outflow.
• Fixed a crash in the opening of the keyframe editor when the object previously held by it has been deleted.
• Fixed an issue where connecting two solvers, one thermally active the other thermally inactive, to a heat flux sensor would lead to a crash in multiphase simulations.

[4.3.0] - 2020-10-30

Added

Preon solver:

• Added a new experimental solver type “DFV/DIP” that supports fast and continuous local refinement.

Sensors:

• Heat flux sensor: Added the properties track avg. heat flux and track avg. HTC that compute the average heat flux or HTC per sample point over an elapsed time period.
• The height sensor now also optionally exports the normals that have been used to preonpy.BufferSets or CSV files.

Sources:

• Added the properties use max volume and max volume to the volume source that can limit the amount of volume that is generated by the volume source.

Plot dialog:

• Added a button to reload data from hard-disk.
• Added a checkbox to make persistent selections.
• Added a checkbox to show only selected statistics.
• Added a filter field to quickly find a certain statistic.
• For each statistic, it is now possible to choose the unit used for drawing the plot.
• Improved the numerical precision of the averaging computations.

Keyframe editor:

• Added a right-click action to define loops over arbitrary many keyframes. The keyframe interval is repeated until a defined point in time. Multiple non-overlapping loop intervals can be defined per keyframe sequence.
• Added a right-click action to move the selected keyframes by a specified time.
• Added a right-click action to duplicate the selected keyframes and move them by a specified time.
• The keyframe editor now also shows the values of the keyframes in the table.

Property editor:

• Improved the workflow for the property editor when having selected multiple objects. If the properties differ from object to object, all property values are shown now. It is now furthermore possible to change a single dimension of a vector for all selected objects at once. Also, right-click actions are now applicable in multi-selection mode.
• Keyframe-related right-click actions are now also available for subproperties (e.g, the x,y and z subproperties of the position property).

Scene inspector:

• It is now possible to rename objects through the Scene Inspector by double clicking or pressing F2. Navigation using tab in edit mode is also supported.

Miscellaneous:

• Airflow import dialog: Added the possibility to smooth Ensight Gold input data.
• Airflow import via Ensight Gold: Samples with identical positions are merged into one sample per geometric part and their velocities are averaged. This can prevent an endless loop when using the Gridless mode as velocity storage implementation.
• Added the possibility to set a custom log directory for PreonNode and PreonCLI via the --logDir option.

PreonPy:

• particle_buffers() can now be accessed for the Snow Solver.

Changed

Preon solver:

• Particles deleted because a NaN value occurred in their position now contribute to the particles deleted by solver statistic.
• Most performance timings are not available anymore as per-solver statistics. Instead, the summed effort across all Preon solvers is now reported in the scene statistics for various solver steps.

Miscellaneous:

• Airflow import: Added support for frame number wildcards as part of the file extension for transient data.
• Changed the property name live csv export to live CSV export.
• Changed the property name csv file to CSV file. This read-only property is only available in PreonPy.
• Changed property name noninear damper coefficient (rear) to nonlinear damper coefficient (rear).
• Removed the record statistics property.
• The data on the hard disk is now immediately deleted when closing an untitled scene instead of when a new untitled scene is created.
• Open boundary planes can (and must) now be connected to a specific solver via the BoundaryDomain slot.
• Improved the accuracy of the velocity prediction method used by the car suspension model that influences two-way coupling with the fluid.
• The installers now suggest “PreonLab VERSION” as start menu directory name on both, Linux and Windows, where “VERSION” is replaced by, e.g., “4.3”.
• The installers now suggest “@HomeDir@/PreonLab_VERSION” (Linux) and “@ApplicationsDirX64@/PreonLab_VERSION” (Windows) as installation directories where “VERSION” is replaced by, e.g., “4.3”.
• Changed the Python version shipped with PreonLab and PreonCLI from 3.5 to 3.8.
• Removed the specify thread affinity option from the scene settings.
• PreonNode now allows up to 4 instances running on the same machine when not passing --noPerformanceChecks. This allows to spawn one process per socket on most multi-socket systems without passing --noPerformanceChecks.
• Renamed the render mode option smoothShaded to visible.
• Renamed the coloring properties for solids and fluids, e.g. TemperatureBased is now called temperature. You can still use the old names in PreonPy.
• Removed the obsolete Mesh particle sampling method for solids.
• Changed the font to Liberation Sans for all platforms.
• In the property editor, when changing a number the arrows for increasing/decreasing the value are removed.

Plot dialog:

• Selecting multiple statistics simultaneously using mousedrag, SHIFT or CTRL, is now possible. Consequently, the checkboxes for multi-selection are removed.
• The statistic plot is now also updated when the “Delete Simulation data before/after current time” action is performed.
• Plot max value elevated to approx 10^12 which influences the keyframe editor too.
• Units are now included in CSV file export in the header line.
• The smoothing width parameter is not upper-bounded anymore. Large smoothing width may decrease the plot dialog performance, though.

Message window:

• Improved the look of the Messages tab in the tab bar when new messages are available.
• Changed the color of warnings and errors.
• The text in the message boxes is now selectable and, thus, copyable.

Keyframe Editor

• Spline interpolation is not applied to imported keyframe sequences anymore by deafault. Instead, linear interpolation is applied.
• Removed the icons for locked and keyed properties to save space. Keyed properties are now printed in bold.
• The values of the keyframes can now be edited directly inside the table. This also allows to set the value of a single changed cell to all selected cells by holding CTRL while confirming the change.
• When switching between objects, the same property stays selected in the keyframe editor as long as it exists for the newly selected object.
• The curve type can now be changed in the key table.
• Improved the performance when importing keyframes from a CSV file.
• The add buttons is now only enabled when correct values are inserted. Furthermore, if the x-axis is not mapped against time, the placeholder text in the x-axis field shows the expected unit.
• Improved the overall layout of the keyframe editor.
• The property list is sorted alphabetically now.

Optimized

• Improved the performance on Windows by up to 15%: The Snow Solver performance is particularly affected and performance improved by up to 50%.
• Slightly improved the performance for multiphase simulations or simulations with local refinement.
• Slightly improved the performance of the implicit thermo solver when using MPI.
• Improved the performance of the implicit viscosity solver when using MPI by up to 15%.
• Improved the performance of the snow solver when using MPI by up to 15%.
• Improved the performance when using local refinement and MPI by up to 25%.
• Improved the height sensor performance in scenes with large geometries.
• Improved the performance in scenes with many sensor planes.
• Keyframe editor: Improved the performance when importing keyframes from a CSV file.
• Selecting many objects in the scene inspector is now faster.

Fixed

Snow Solver:

• The Snow Solver warm start option now converges to a more similar result and can lead to lower iteration counts.

Sources:

• Fixed an issue that the Area source didn’t emit any particles when using a flat jet area with a very small fan angle.

GUI:

• Graphics window: Fixed that the clipping plane could not be scaled with the asymmetrical dragger.
• Keyframe Editor: Fixed that the same frame was loaded multiple times when having “Update time on click” enabled and moving the clicked mouse in the graph.
• Plot Dialog: Title (and names of stats when multiple objects are shown) are updated when an object is renamed.
• Plot Dialog: Unit is updated for the current value.
• Property editor: Fixed that for a new scene, the properties show sim statistics, show timings, and track memory were shown as deviating from the default.
• Property editor: The unit of revolution is now correctly displayed to be dimensionless.
• Property editor: The revolution start property now allows the full range of real numbers as input.
• Timeline: The green marker in the timeline is now instantly created/moved as soon as the corresponding keyframe is created/moved in the keyframe editor.
• Timeline: Fixed issue that the marker sometimes did not update correctly while simulating when using different view and simulation frame rates.

Miscellaneous:

• Airflow import: Fixed an issue that transient geometry would be interpreted to be static if the optional timeset number was missing in the model description of the Ensight Gold case file.
• Fixed an issue where the file extension “.CSV” (upper case) would not be recognized as a valid import or export file for CSV on Windows.
• The adhesion property is now also reset if applying the default physics preset to a solver.
• Fixed that providing a start time that is larger than the end time to PreonNode did not result in an error.
• When PreonCLI is started to process a scene, no intermediate untitled scene is created. This helps to prevent some error messages if no home directory is available.
• Added a clipping input slot to the distance sensor thus allowing it to be clipped.
• Fixed possible exception when using an inactive solver that is connected to an active solver via the refinement connection.
• Fixed possible crash when loading a fluid “.prstate” file from a network drive with unstable connection.
• Fixed a Volume source issue that when using the Badpoint connection, the “bad path” was not fully drawn to the seedpoint.
• PreonMesher does not print an error message anymore when being active during a simulation without fluid particles.
• Fixed a rare crash that could occur when simulating after deleting a heat flux sensor.

Removed

• Removed the partio particle export library. This removes the possibility to export particles into formats like “.bgeo”. EnSight Gold and CSV exports are not affected. If you need to export into the formats that have been removed, you can use the partio Python interface together with the PreonPy buffer access.
• Removed support for RHEL 6.x.

Deprecation notices:

• PreonLab 4.3 will be the last version that supports Python 3.5, since the Python project announced the EOL of this version to be in September 2020. We still support 3.6, 3.7 and 3.8. Note that most likely you don’t have to change your code, since those minor versions are largely backwards compatible. You though have to update your Python installation if you used Python 3.5.

[4.2.4] - 2020-08-07

Fixed

• Fixed a memory issue that could occur when using a seedpoint-filling object (Volume source, Area source, Volume sensor or Box domain). In rare cases, this issue could lead to crashes and/or excessive memory consumption.
• Fixed an issue that the no gap property was not synchronized between different solvers in multiphase setups.
• Fixed an issue that the Thermodynamics::implicit property was not synchronized between different solvers in multiphase setups.

[4.2.3] - 2020-07-17

Fixed

• Fixed an issue in the airflow import from Ensight Gold geometry files. The format employs 1-based indexing, but was considered to be 0-based in the importer.
• Fixed a crash when using local refinement and MPI.
• Improved the error logging when PreonNode terminates due to not enough memory.

[4.2.2] - 2020-06-26

Fixed

• Fixed an issue that the Badpoint connection offered by the volume source did not work.
• Removed Badpoint and Align connecition input slots for the volume sensor and the box domain (these are only available in the volume source).
• Fixed a bug that could lead to wrong simulation results and to rare crashes when inserting new objects while single-stepping through a simulation.
• Fixed an issue that setting an open boundary plane to inactive had no effect.
• Improved the stability of the snow solver when snow is in contact with boundary.

Optimized

• Improved the performance of the airflow import via the Ensight Gold format.

[4.2.1] - 2020-06-08

Fixed

• Fixed rare crash that could occur when using the force sensor in combination with dynamic sampling.
• Fixed an issue in PreonPy and PreonCLI that the open boundary plane was placed wrongly when its default transformation had been changed. PreonLab was not affected by this.
• Added more load balancing statistics to the Mpi domain useful for performance analysis.
• Fixed an issue in the experimental Impulse Boundary Handling where particles collided too early and were left out by the Snow Solver.

[4.2.0] - 2020-05-28

Added

Domains

• The box domain now supports seedpoint-defined volumes similar to the Volume sensor and the Volume source.

PreonPy:

• Added parameter force_overwrite to the save function of the preonpy.Scene class.
• For rigids, compute system and its complement reset pivot have been added to the API.

Rendering:

• Added option render single particles to the Surface material that switches between particle and surface rendering for fluids.
• Added option light sources factor to the Surface material that weights the contributions of light sources in the scene to the material.
• Added option headlight factor to the Surface material that can be used to illuminate the material from the camera’s point of view.
• Added presets for the Surface material for fast and high-quality fluid particle rendering.

GUI:

• Objects in the Scene Inspector can be filtered by entering substrings of object names into a search box.
• Added right-click actions that allow to quickly show/hide a) selected objects b) (selected) objects of a specific type or c) all objects of a scene.
• In the keyframe editor, it is now possible to extend or scroll the property table in case of long property names. Scrolling is only enabled in the presence of long property names.
• Statistic values in the OSD are now shown in a tabular representation.
• Physical units in the OSD are now formatted using the same representation as in the property editor.
• In the property editor, the range for coloring cannot be changed anymore when automatic range is on. Previously, they could be changed, but were immediately overwritten by the auto-computed values.
• In the property editor, the “copy PreonPy name” action is not displayed anymore for elements of composites such as the single dimensions of the position property.
• Added a link to the PreonLab Manual in the Help menu.
• Properties that vary amongst particles, like the rest density are not hidden from the property editor anymore when temp. based density is enabled. They are shown now, and in place of the property value, a link to the keyframe editor is offered.
• Video export dialog: Added a button to copy the current FFmpeg command to the clipboard.
• Added the possibility to display tooltips while hovering over dropdown menus in the property editor. This is for example used for the Preon solver properties viscosity model and the experimental solver type.
• The “Reset Pivot” command now properly supports undo.

Preon solver:

• The implicit viscosity solver and the thermo solver now support local refinement.
• Added experimental error relaxation property which stabilizes multiphase simulations to allow simulations with high density ratios.
• Added experimental solver type property which allows to select the DI/PS variant. This variant allows to compute an additional position shift step for the fluid particles that does not influence velocities after the default density invariant solver step.

Air flow:

• The Air flow force field now has a new property velocity storage implementation that offers a new gridless mode (this mode is also the default for new scenes). The gridless mode consumes less memory and offers more accuracy than the grid-based approach, but requires more computational power during the simulation.

Snow:

• The solver will now fall back to an alternative solution if the implicit solution did not converge. It fixes instances of heavy particle deletion and explosions.
• Added experimental Coefficient-of-Restitution-based boundary handling.

Height sensor:

• Added mesh-based height sensor to measure fluid thickness on top of a solid. The sensor supports multiple solvers.

Rigid body solver:

• The automatically computed inertia tensor is now displayed in the property editor and can be queried in PreonPy. Note that the value is only correct after the simulation has been started.
• When using the RBPS, it is now possible to manually specify an inertia tensor for dynamic objects.

Sources:

• Added new fill method quality that minimizes the amount of artificial void spaces in the generated sampling due to particle discretization. This also gives much more consistent results across different fluid resolutions.
• You can now connect one or multiple seedpoints to an Area source.
• Added a right-click action “Add seedpoint” for the Volume source and the Area source.

Car suspension model:

• Added parameter reference point that allows to relate zero spring deflection to an uncompressed spring, or the spring configuration under axle load.
• Added parameter mapped unit that allows to specify the unit of the quantities the deflection is mapped against if non-linear spring modelling is enabled.

PreonNode / PreonCLI

• Added --postprocess option. This allows to postprocess a given scene instead of simulating it, e.g., for rendering. Note that this always postprocesses all active sensors/renderers, i.e., previous sensor data from the simulation may be overwritten.

Miscellaneous:

• Added experimental Open boundary domains.
• Added experimental Open boundary plane.
• Transient airflow import via the EnSight Gold format: Added support for static geometry files.
• The PreonCLI and PreonNode help text now contains additional information about environment variables and a link to the manual.
• Airflow import via the EnSight Gold format: The element types ‘nsided’ and ‘nfaced’ are now supported.
• For objects that support thermodynamics, system types that are not valid for the specific object type are not selectable anymore from the GUI.

Changed

PreonNode

• Running PreonNode with two instances on one machine now also produces an error (unless the --noPerformanceChecks option is given). Before, this error was only shown with three or more instances.

Preon solver:

• The simplification algorithm for local refinement will now only merge particles with similar velocities, which improves overall simulation quality.
• The simplification algorithm is now also executed independently of refinement. However, it is only executed if there are enough simulation steps since the last simplification to ensure good performance.
• Tweaked default refinement buffer zone settings in the collider settings to allow for more precise refinement and simplification.
• Local refinement now preserves the density and pressure field of unaffected regions in the fluid more accurately.
• Replaced the power-law viscosity model by the more general Herschel-Bulkley model. If the yield stress and stress growth exponent properties are set to zero, this equals the previous power-law model.
• The user-defined timestep property, which is used if Time Stepping->adaptive is off, is no longer overwritten by PreonLab if Time Stepping->adaptive is on.
• The property temperature has been removed from the solver. If you want to set a temperature for all currently existing particles of a solver, use the new right-click action Set temperature.
• The timestep property is now keyframeable. Furthermore, the visibility of maximal timestep property is now correctly updated in the keyframe editor.
• Improved viscosity behavior in simulations containing multiple fluids with different densities.
• Local refinement may not be employed in multiphase simulations.

Snow:

• Changed the default shear friction factor from 10 to 1.
• Changed the default stuck threshold from 1.25 to 0.9.

Sources:

• Moved Volume source properties related to volume generation to property group Volume settings consistent with the Volume sensor and the Box domain.

Sensors:

• Newly inserted sensors now connect to all fluids by default.
• Improved numerical accuracy of summed sensor plane statistics (like average velocity).
• It is now possible to choose a cell size for the air flow visualizer manually. The cell size is still automatically synchronized with the airflow cell size if the airflow uses a grid-based velocity storage.

GUI:

• Connection editor: The filter types become scrollable if the size of the connection editor dialog would otherwise be too large to be fully displayed.
• Connection editor: “Center on selected objects” now also zooms in.
• In the property editor, the “Set to default value” command is now also applicable to groups, resetting all of the properties in all of the subgroups to the default value.
• In the property editor, the “Set to default value” command is now only visible if the current property value differs from the default value.
• In the property editor, it is now possible to enter numbers with up to 17 digits. Previously, this was limited to 7 digits.
• In the property editor, the , character is now also accepted as decimal separator.
• Presets are now listed in alphabetical order in the context menus on all platforms.
• The user preferences, collider settings and rigid body settings now use the same look&feel as the property editor. This brings multiple advantages: Grouping of properties, undo/redo and improved input of values all behave similarly. Furthermore, the respective dialogs can now stay open while being able to continue to work in PreonLab.
• Connection editor: It is not possible anymore to zoom the connection editor such that all objects disappear.
• Fixed an issue that on several places in the GUI, for real numbers whose decimal part matched the integer part, only the integer part was shown and the decimal part was omitted.
• All number input fields in all dialogs now accept and display the same number of decimals. Previously, some inputs field, including the ones in the keyframe editor, only allowed to input and to show a limited number of decimals.
• In the keyframe editor, using the “Fit to curve” button now fits the whole curve and not only the keyframes.
• Fixed an issue that long camera names got cropped in the rendering dialog.
• The smallest unit shown for time statistics is now always rounded down. This fixes an issue that for example “1m:60s” was shown.
• If a solid´s triangle mesh is connected to multiple sensors, the mesh coloring is decided among active and visible sensors in the following order: Force sensor, heat flux sensor, height sensor, wetting sensor.

Rendering:

• Inactive cameras connected to a renderer are no longer rendered during simulation or postprocessing.
• Tweaked the snow_fast material preset so that it matches the snow_quality preset a bit closer.

Car suspension model:

• Removed the property compute initial deflection.
• Inverted the sign of the statistics Front_SpringForce, Rear_SpringForce, Front_DamperForce and Rear_DamperForce.

Miscellaneous:

• Increased the default value of segments of the sphere object to 52 and moved the property to the General group.
• Removed the timestep property of the scene.
• Improved the error handling when reading or writing statistics from / to disk failed.
• Copy&paste of objects: Default connections are created between existing objects in the scene and the pasted objects. Note that this process might create connections for the copy that you have previously removed from the source.
• When using the animation import, it can now be selected if the imported keyframes should use linear or spline interpolation.

Optimized

Preon Solver:

• Significantly reduced the computational cost of local refinement for cases in which only parts of the fluid are affected.

MPI:

• Slightly optimized MPI performance in scenes with few particles.

Sensors:

• Improved Sensor plane performance for some scenes.
• Improved Force sensor performance when using the no-gap boundary handling option.

Miscellaneous:

• Reduced memory consumption by solid particles when not simulating rigid body dynamics.
• Significantly improved performance in scenes with very large geometries (compared to the fluid) and dynamic sampling enabled.
• Improved performance in scenes with many objects.
• Reduced the memory consumption of the Volume source by a factor of up to 2.
• Slightly improved snow solver performance by using better scheduling for snow particles in contact with boundary.
• Improved the numerical precision of various calculations, including object transformations.

GUI:

• Improved the efficiency of the connection editor for object groups in scenes with many objects.
• Improved GUI performance when right-clicking on a group in the scene inspector and choosing Select all children.
• Fixed a bug that choosing “Show Curve” in the property editor would not switch the chosen property in the keyframe editor if the keyframe editor was already open.

Fixed

Preon solver:

• Fixed an issue that friction forces and temperature diffusion were sometimes inaccurate when using the distance correction/distance correction thermo options.
• Fixed an issue in the temperature-based density computation. This is only relevant when using thermodynamics and temperature-based density.
• Fixed a rare issue with stable initialiation resulting in wrong particle velocities if integration time step is clamped.
• Fixed a determinism issue when using local refinement and simplification.
• Fixed an issue that setting the behavior of a refinement domain to inactive did not prevent the particle refinement to take place.
• Corrected a prefactor in the power law viscosity model (which is now part of the more general Herschel-Bulkley model), which led to deviating simulation results in some cases.
• Fixed an issue in the PotentialForce cohesion model that resulted in same accelerations for different rest densities.
• The Rendered particles statistic is now only shown if particle downsampling is active.

Snow:

• Fixed the snow behavior for area sources: Snow emitted by an area source was almost immediately plastic.

Rigid body particle solver:

• Fixed a possible crash when keyframing the rigid type of a rigid body from dynamic to scripted.

Rendering:

• It is not possible anymore to enter invalid values (like “-1” for specular to diffuse ratio) for material properties using the property editor.
• Fixed an issue that rigids with enabled mesh coloring connected to a material with enabled override color were lighted differently in the graphics window than when rendered using the Preon renderer.

GUI:

• Fixed an issue that “Jump to last simulated frame” jumped to the wrong frame while being in playback mode and simulation and view frame rate differed.
• Fixed an issue that checkboxes were shown instead of radio buttons.
• Fixed an issue were selection of an edge in the connection editor was not possible.
• Fixed the issue that long tooltips for properties without units being displayed without line breaks.
• Fixed the issue that tooltips were not shown for right-click actions in sub menus.
• Fixed an issue in the connection editor that lead to objects being drawn upside down zooming out too much at once.
• Whitespaces are now removed when inputting time, e.g., ” 3 s ” is now correctly interpreted as 3 seconds.
• Fixed the issue that very large time values and very small time values (<1ms) were not correctly displayed.
• Fixed the issue that the property editor sometimes did not show the correct property values when selecting multiple objects.

MPI:

• Fixed a warning when compiling preonmpiadapter.
• Fixed a synchronization issue when using local refinement.
• Fixed an issue when using the quality cohesion mode that could lead to inaccurate simulation results.
• Fixed exception being thrown when using multiple force sensors with enabled substep updates connected to dynamic rigid bodies simulated using the RBPS.
• The CFL time step solver statistic is now reduced correctly across all worker nodes.
• The num simulated particles statistic of the Preon Solver is now summed up across all worker nodes.

PreonPy:

• Fixed the color property return type.
• Fixed that the post_process command aborted too early if view and simulation frame rate differ.
• Fixed that the post_process command did not correctly generate data for pathlines.

Miscellaneous:

• Fixed a rare crash when scaling a solid with dynamic sampling enabled.
• Fixed that changes to the user preference “save scenes before simulation or post-processing” were not stored.
• The setting “save scenes before simulation or post-processing” now yields a scene save if any rigid samplings have changed, too.
• Fixed an issue that the cache marker in the timeline of an Alembic Mesh did not immediately update when the animation time factor was changed.
• Fixed an issue that the cache marker was placed incorrectly when the animation time factor was anything other than 1.
• Fixed a rare issue that solid particles could go out of sync with the solid geometry with dynamic sampling activated.

Removed:

• Removed support of PreonPy for Python 2.7.
• Removed “Preon Solver (3.3 settings)” for the creation of a solver object. Old scenes will still load as expected.

Deprecation notices:

• 4.2 will be the last version that supports RHEL 6.x. Note that if you use other Linux based operating systems that are not officially supported, this may also affect you. If you are uncertain, please contact our support. We can provide a special version that can be used to test OS compatibility already before the next release.
• The rigid body simulation library Bullet will be removed in the next version after 4.2. Instead, the rigid body solver particle (RBPS) can be used.
• The partio particle export library will be removed in the next version after 4.2. This will remove the possibility to export particles into formats like .bgeo. EnSight Gold and CSV exports are not affected. If you need to export into the formats that will be removed, you can use the partio Python interface together with the PreonPy buffer access.

[4.1.6] - 2020-04-29

• Fixed mesh-based volume sensor issues when using dynamic transformations and / or local refinement.
• Fixed issue that the mesh-based volume sensor didn’t use multithreading.
• Fixed the problem that changing the path to a geometry file in the property editor was not effective in certain cases.
• Fixed issue that leakage could occur in simulations with a spacing lesser or equal than 0.001 and when using one of the primitive shapes (sphere, cylinder etc.) with “sample trianlge mesh” disabled and “dynamic sampling” enabled.

[4.1.5] - 2020-04-03

• Fixed possible crash when using local refinement, MPI and domain-guided particle scripting at the same time.
• Fixed rare issue that the computed timestep could be zero.
• Fixed crash that could occur when deleting and reinserting a sensor mesh.

[4.1.4] - 2020-03-04

Fixed

• Fixed issue that could occur when using dynamic sampling and particle-based mesh coloring (used by the force sensor, the sensor mesh and the wetting sensor).
• Fixed possible crash when using local refinement and MPI.

[4.1.3] - 2020-02-19

Fixed

• Fixed issue that performance could decrease over time in scenes with a high number of simulation substeps.

[4.1.2] - 2020-02-14

Fixed

• Fixed issue that the “Create refined solver” right-click action was only visible in experimental mode.
• Fixed an issue that a simulation or playback start time >10s would not be loaded from the .prscene file.

[4.1.1] - 2020-01-23

Fixed

• Fixed an issue that the refinement output slot of domains was only visible in experimental mode.

[4.1.0] - 2020-01-17

Added

Sensors:

• Added support for multiphase simulations and local fluid refinement to the sensor plane and the sensor mesh.
• Added support for local fluid refinement to the force sensor and the wetting sensor.
• Added support for substep updates in MPI mode to the sensor plane and the sensor mesh.
• Added support for substep updates in MPI mode to the force sensor. However, per-particle max pressures are still only tracked at full frames.
• The heat flux sensor now supports MPI (however no substep updates yet).
• The sensor plane and sensor mesh now also measure the normal velocity.
• The sensor plane now has optional arrows to indicate its orientation and flow rate mode. The arrow color for positive/negative flow rate is customizable.

preonpy:

• Added buffer export functionality for force sensor, sensor mesh, sensor plane, wetting sensor and heat flux sensor buffers.
• Added support for Python 3.6, 3.7 and 3.8.
• Added the possibility to force a statistics reload. This can be used to obtain them when they were changed by another instance or in scenes opened with the load_only_object_creations flag to get statistics.

MPI:

• In case of a fatal MPI synchronization issue, PreonLab will now write accurate debug information to the log files automatically. In many cases, this eliminates the need to rerun everything with the –debugLogging option.

GUI:

• In the property editor, it is now possible to reset a property to its default value via the context menu.
• In the property editor, the background of keyframed properties is now colored depending on the state of the property.
• In the property editor, the physical unit is directly displayed after the value for physical properties.
• In the property editor, groups containing modified properties are now also accentuated in bold.
• Harmonized the look & feel of PreonLab across different platforms.
• Added a right-click action for transform groups which rotates their coordinate systems such that one of their axes is aligned with two points provided by the user.

Rendering

• Added property “fade factor” to the surface material that is multiplied to the overall opacity of the object and allows to easily realize fade-in and fade-out effects via keyframing.

Miscellaneous:

• The single particle tracker now plots the determinant of matrix values of particles.

Changed

Preon solver:

• Slightly reduced the number of deleted particles in some scenes when using the “no gap” boundary handling option.
• Local refinement is no longer marked as experimental.

Snow:

• Improved the performance and stability of the snow solver. For this, the default values of newly inserted solvers have been adapted. If you have stability issues, please enable experimental mode in PreonLab and check the settings in the Numerics property group.
• Removed some experimental properties of the snow solver (script source particles, delete high value particles, snow accel. time step factor, Explicit and PredictedExplicit modes for experimental solve type property).
• Reduced the amount of data that is written to disk each frame. This change also means that it is not possible to use the force sensor in a post-process step for simulations done with 4.0.
• Added an experimental warm start option for the snow solver which can increase performance.
• Single snow particles look less like a sphere due to reduced specular highlights and less diffuse lighting based on light direction.
• Tweaked the snow subsurface scattering approximation to minimize flickering.

Sensors:

• The Volume sensor now supports user-defined volumes similar to the Volume source (for instance using seedpoint filling). This feature replaces the experimental volume sensor-source coupling introduced in 4.0. Please note that there is no automatic scene upgrade for old experimental volume sensors created with PreonLab 4.0.
• Removed the “smooth no-gap pressure” option for the force sensor. If no-gap is used, the force sensor now automatically uses an improved smoothing method.
• The heat flux sensor employs an improved smoothing method in applications where the no-gap option is enabled in the Preon solver.

preonpy:

• The type preonpy.BufferSet got renamed to preonpy.BufferSetRef.
• The area source property precipitation height ("mm/min") got renamed to precipitation height.
• When opening scenes with the load_only_object_creations flag, the scene statistics are not loaded by default. Please use the new reload_statistics method.

Miscellaneous:

• The “color” property of a fluid solver object is now only displayed if the coloring mode is set to “None”. The “Coloring” group is only displayed if the coloring mode is not set to “None”.
• When using an adaptive timestep for fluids, the “timestep” property is not shown anymore, as it cannot be changed by the user. Only the “max timestep” property is visible in that case.
• Removed the “particle limit” for Solids in case the dynamic sampling is used.
• Extended the set of valid characters for object names from the set of alphanumeric characters to all printable ASCII characters (excluding those which are reserved by the file system).
• Changed the name of the “deterministic” commandline argument to “particleBasedLoadBalancing” in order to be more descriptive.
• The video export now produces variable bit rate videos. This results in smaller file sizes while retaining quality. Instead of asking for the constant bit rate, the video export dialog now allows to choose a quality mode from given presets.
• Keyframes are now exported to CSV in the Keyframe Editor using the property name as displayed in the Property Editor.
• When using dynamic boundary sampling, the “Delete data” timeline action and the python method “reset_simulationdata” now also clear any dynamically generated rigid particles.
• Air pressure object: It is now possible to keyframe the air pressure depending on the distance from the center of the air pressure object.
• Exposed the adhesion property in the Preon solver which defines the adhesion between different fluid phases.
• Manually inserting an MPI domain (which is only useful for debugging) is now an experimental feature and is not exposed by default.
• Renamed the snow solver property intial Young Modulus to Young Modulus.

GUI:

• Improved the support for HiDPI monitors.
• On/off properties in the property editor are now displayed using a switch-like visual representation.
• When editing the name of an object with the property editor, the name only gets updated when editing finishes. This simplifies editing of names, as there are no invalid intermediate states when changing the name anymore.
• Read-only properties are now grayed out in the property editor to better distinguish them from editable properties. Furthermore, they are not shown anymore when having selected multiple objects.

Optimized

• Improved the performance in scenes with few fluid particles when using “dynamic sampling” on a large rigid.
• Improved the Preon solver performance when using the “Quality” cohesion mode by up to 20%.
• Improved the post-processing performance for scenes with multiple heat flux sensors.
• Optimized the disk consumption for mapped static temperature point clouds on solid objects. In this case, the temperature buffer now is only stored once and not per simulation frame.

Fixed

Sensors:

• The force sensor now measures adhesion forces correctly when using the “PotentialForce” model and the “Quality” performance mode.
• Fixed an issue that the “max pressure” statistic of the force sensor was not displayed correctly in the plot dialog in some cases.

preonpy:

• Fixed an issue that calling ‘write_statistics_to_csv’ with ‘fixed_time_interval’ set to ‘True’ would always employ the default view framerate.

GUI:

• In the property editor, it is not possible anymore to insert values that are outside of the range of the property.
• Fixed an issue in the keyframe editor that a sequence of keys using spline-interpolation was not displayed accurately when the distance between the keys was very low.
• The “preonpy documentation” button in the console now links to the documentation of the current version. Previously, it pointed to the documentation of an older version.

MPI:

• Fixed a possible crash when using MPI and local refinement.

Rendering:

• Fixed a minor issue in the surface material that indirect diffuse lighting was ignored when a skylight factor of 0 was used.
• Reduced a flickering issue in the snow rendering that could occur given certain lighting configurations.
• Fixed some visual artifacts in the Preon Renderer that could occur in large-scale scenes.
• Fixed an issue in the renderer that use scene background was keyframeable after toggling transparent background twice.
• Fixed a shader crash when copy-pasting the DefaultMaterialFlat and a light source into the scene.

Miscellaneous:

• Fixed an issue in the computation of the local heat transfer coefficient in multiphase simulations.
• Fixed an issue that keyframes were not correctly saved or copied when inserting an invalid value (e.g., -1 for behavior).
• Fixed an issue that the right-click action “Export particles” for the Preon solver did not find any particle data after simulating.
• Fixed an issue that no undo event was created if the user switches the transformation mode while dragging the transform modifier (e.g. translating along the x-axis).
• Fixed an issue in the per-particle pressure initialization for the Density Invariant Solver in the PreonSolver after a manual frame jump in the timeline.
• Fixed a rare crash when importing an Alembic mesh.
• Fixed an issue where an inactive airflow visualizer would try to display old sensor data.
• Clipping objects don’t clip light sources anymore.
• Removed keyable color properties that should not have been keyable.
• Fixed an issue in the computation of the surface area of the heat flux sensor.
• Fixed an issue where all entries of a group got partially checked as soon as the group itself was set to partially checked when opening the “Save As” dialog.
• Fixed an issue that the lookup table for non-linear spring or damper coefficients would not be employed due to the table having allegedly too many entries.
• Fixed an issue in the Car Suspension Model that occurred when switching from non-linear spring/damper coefficients back to linear constants and the deflection/velocity-based coefficient mapping would be interpreted as a time-based mapping.
• Fixed an issue that the solver statistic ‘Ave-Density’ could show a higher value than the solver statistic ‘Max-Density’.

Deprecation notices:

• Version 4.1 will be the last version that supports Python 2.7.

[4.0.3] - 2019-11-20

Fixed

• Reverted version of the progressbar2 package to the one shipped with 4.0.1.
• Fix preonpy, so that it can be used with newer versions of the progressbar2 package.
• Fixed keyframe CSV-import issue that prevented composite properties (e.g., “position x”, “position y”, …) from being imported.
• Fixed some parts of the preonpy API documentation.

[4.0.2] - 2019-10-30

Fixed

• Fixed an issue in the CSM import of non-linear damping coefficients.
• Fixed a crash of PreonNode and PreonCLI when the --lList option was used and no license file was available at all.
• Fixed a problem where a cached information about which frames were simulated was out of sync. This resulted in warnings about missing simulation data in the PreonLab GUI.
• Fixed an issue in the automatic computation of inertia tensors.
• Fixed cohesion issue when using the local refinement and MPI.

[4.0.1] - 2019-10-08

Fixed

• Fixed possible performance issue in the graphical user interface when loading a scene with many objects.
• Fixed an issue that an area source connected to an outflow domain did not emit enough fluid in some cases.
• Fixed performance issue when the RBPS was selected as rigid solver (which is the case by default for new scenes). This fix also affects scenes without any actual RBPS calculations.
• Added property “cell limit” to the AirFlow that sets the maximum number of cells (in millions) for the top grid level to prevent allocation of too much RAM.
• Fixed an issue where a progressbar could potentially stay visible during simulation.
• Fixed stability issue for area sources emitting into refined regions.
• Fixed an issue in the CSV import of keyframes.

[4.0.0] - 2019-09-23

Added

Preon solver:

• Added implicit solver for thermodynamics.
• Added new “FluidRefinement” input and output slot for the Preon Solver. A refinement output solver has coarser particles that will be subdivided and transferred to the corresponding input solver when they enter a connected refinement domain.
• Added new “RefinementDomain” slot that allows to connect Boundary domains to Preon Solvers for the purpose of refining coarse particles. Fine particles outside the domain may be simplified into coarse particles.
• Added new “PotentialForce” cohesion model, which is calibrated to use the physical parameter of surface tension.

Snow:

• The snow solver now supports multiphase simulations (i.e., multiple snow solvers can be used in a single scene).
• Added and exposed more properties for the snow solver. Also changed default settings for newly inserted snow solver to be more robust and allow larger time steps.

Sensors:

• Added a heat flux sensor which can be connected to a solid object. In addition to the heat flux, the heat transfer coefficient is evaluated, too.
• Added a ‘SensorPlaneTemperature’ input slot to the heat flux sensor that allows to derive the heat transfer coefficient from the surface temperature of a solid and the fluid temperature measured by a sensor plane.
• You can now connect a Volume source to a Volume sensor via the new VolumetricObject slot. In this case, the Volume sensor will only measure fluid in the volume defined by the Volume source (for example using seedpoints).
• Added the possibility to switch the shape of the Volume sensor between ‘Box’ and ‘Cylinder’.

preonpy

• Added direct access to particle data without memory copy involved, i.e., direct access to the data structures of PreonCore.
• preonpy now supports all presets.
• Added crop_left and crop_right methods to the scene object.
• Added the methods get_resource_files and is_portable to the scene object for automating cluster-related tasks easier and more robust.
• The PropertyNotFound exception now contains a more helpful message if the property got renamed.

MPI:

• The rigid body particle solver now supports MPI.
• The snow solver now supports MPI.

GUI:

• Introduced a new “Save As” dialog which allows by-category selection.
• Property values which differ from the default value are now printed in bold in the property editor.
• The tooltip for all PreonSolver properties now shows the physical unit of the property, as well as its range.
• Added a right-click action to copy the property name for preonpy access. This name may differ from the name shown in PreonLab in order to avoid name collisions. If the name differs, this will also be shown in the tooltip for this property.
• Added right-click action “Jump to last simulated frame” to the timeline.
• Added a user preference to automatically save the scene when starting to simulate or post-process.
• Keyframed properties are now colored yellow in the property editor.

Rendering:

• Added optional subsurface scattering approximation to the surface material (works currently only for fluids).
• Added optional procedural noise generator to the surface material (works currently only for fluids).
• Added snow material presets for the surface material that make use of subsurface scattering and noise generation.
• Added an option to ignore transparency of the background for secondary rays.
• Added parameter “enable diffuse reflections” to the Surface material that allows to simulate indirect diffuse lighting.
• Added parameter “skylight factor” to the surface material that weights the hemisphere color during indirect lighting calculations.
• Added material preset “sensor” that can be applied to meshes connected to a sensor for a reduced influence of light direction.
• Added property “sdf method” to Preon Renderer that allows to switch between different signed distance field computation methods. This feature is still in experimental stage.

Miscellaneous:

• Added a novel “Air Pressure” force field that applies a force in normal direction at the free surface of a fluid.
• Dynamic sampling is now supported for all integrated Solid types except for the Porous Rigid.
• The cuboid, box, capsule, sphere and cylinder now offer a property “sample triangle mesh”. If this is enabled (which is the default), the mesh will guide particle sampling and not the mathematical shape. Mesh sampling is faster for most cases.
• Added property “track memory” for all objects that enables or disables its memory consumption statistic. The property is disabled by default except for the scene and the collider.
• Added use cohesion as adhesion and solid adhesion properties to the Preon and snow solver which can be used together with the new “Potential force” cohesion model if the adhesion specified in the solid should not be a factor of the solver cohesion.
• Added the possibility for piecewise linear spring and damper coefficients in the car suspension model.

Changed

Preon solver:

• Changed the default values for the Preon solver, particularly setting the new cohesion model “Potential force” by default. For getting the previous default values, the newly introduced “3.3 settings” preset must be used.

Snow:

• Improved file compression of snow .prstate files. Please note that snow .prstate files created with 4.0.0 can not be loaded with older version.
• Changed the default settings of the snow solver.
• Removed the solver type selection property of the snow solver. BiCGStab solver is now always used.

Solids:

• Dynamic boundary sampling is now the default for new scenes.
• The RBPS is now the default rigid body solver in new scenes.
• Improved precision of solid particle velocities in cases where keyframing is used.

Sensors:

• The force sensor prints and records only net forces. The local values measured and recorded are pressure and shear stress. For these local minima and maxima are computed as well as the average on the total area defined by the force sensor (connected solid mesh). The net pressure statistic is removed.
• Fixed computation of pressure and shear stress for two-dimensional scenes.
• Added property “smooth no-gap pressure”, that enables or disables the smoothing of measured pressure values when using the no-gap boundary handling option.
• The track max pressure property in the Force sensor is no longer experimental.
• Statistics for saturated wetting are displayed in OSD and plot dialog only if “track wetting time” is enabled for the Wetting sensor.

preonpy:

• Some properties, especially those where we had name collisions before, now have a different unique name for preonpy access.

Miscellaneous:

• Keyframes can now be imported via CSV in the Keyframe Editor using the property name as displayed in the Property Editor.
• Experimental connection slots are now hidden in the connection dialog, if the “experimental features” setting is not set.
• The default position and scale of Area source has changed.
• The default particle spacing of the Preon solver has changed from 5cm to 2cm.
• The default scale of the solid object “Box” has changed from (3, 1, 3)m to (1, 1, 1)m.
• If transient airflow files can not be handled in file copy operations and in preonpy’s Scene.get_resource_files due to a known issue, a warning is printed.
• show time is now enabled by default for Preon Renderer.
• The action “Delete simulation data before/after current time” now removes all types of result files. In previous versions some post-processing files were not deleted. The action also got renamed to “Delete data before/after current time”.
• The action “Delete simulation data” got renamed to “Delete data”.
• Both actions “Delete data before/after current time” and “Delete data”, now don’t delete files not written by PreonLab.
• Changed the name of camera preset “default” to “perspective_default”.
• Upgraded PreonLab’s central structure-of-arrays binary file format, fixing a possible integer overflow issue for very large data sets. This means that .prstate, .prsampling, .pathlines and .prf files created with PreonLab 4.0 can’t be loaded in previous versions. PreonLab 4.0 is still fully backwards-compatible.
• Some internal variables will not be stored in the .prscene file anymore.
• Changed the default installation directory from C:\Program Files (x86) to C:\Program Files
• The right-click action “Regenerate and show preview” for the Volume Source is now called “Regenerate and show volume”.

Fixed

Snow:

• Fixed force sensor and two-way coupling in combination with semi-implicit snow solver. There is still a known limitation that if the system is not solved perfectly, that the force sensor results may differ from the forces applied by the snow solver. This can be improved by enforcing a more perfect solve of the system by setting the stopping criterion to MaxResidual.

MPI:

• Fixed issue when using dynamic sampling in a MPI simulation on one of the integrated solid shapes offered by PreonLab (like Plane and Box).

Miscellaneous:

• Increased the floating point precision to 1.0E-7 for the time column in the CSV export.
• Fixed an issue when applying the wading script to a scene with specific transform hierarchies that surround the car suspension model.
• Fixed typo in iterative solver property: stopping criterion -> stopping criterion.
• Fixed printing of HTML characters in the message dialog.
• Fixed minor determinism issue when rendering snow.
• Fixed that some debug DLLs were distributed with the installer on Windows. This reduces the installer and installed size of PreonLab slightly.
• Fixed rare crash that could occur when simulating or post-processing with a distance sensor.
• Fixed issue that PreonCLI did not consider the number of threads specified in the scene file when rendering.
• Fixed some corner cases where copy & pasting multiple objects previously did not result in the correct connections being maintained.
• The RBPS no longer records statistics if there are no dynamic rigid bodies in the scene.
• Fixed “Clean Data” right click action for Solid objects.
• Fixed an issue that pathlines only showed a part of the lines when restrict lifetime was enabled before disabling playback.
• Fixed issue that the cache marker in the timeline of an Alembic Mesh did not immediately update when the animation offset was changed.
• Fixed an issue that an airflow visualizer connected to a transient airflow was not always updated in time.
• Fixed an issue in the interpolation of transient airflow data.
• When importing or exporting files, the path of the last file chosen in the corresponding dialog window is now correctly stored again, so that it does not need to be entered each time the dialog is opened.
• Removed the property ‘apply scaling on pivot’ from objects that do not expose the pivot or scaling at all.
• When exporting an Alembic file, the .abc file ending is now automatically added when it is not specified manually.
• With air flows, it is now possible to specify whether the sample points shown should be normalized or not. Furthermore, it is possible to specify a scale for their visualization.
• When loading a scene with a “Mesh resource” object and the mesh file is not available, it is now possible to set a new path and have the connections restored.
• Fixed an issue where the force sensor would only consider fluid particles of the first connected fluid object.
• Fixed an issue that occurred if multiple mesh resources shared the same file name and the scene should be saved as a portable scene.
• Fixed an issue where the validator of the Ensight format description file (‘.case’) would return success although an exception has been raised during the validation.
• Particle previews of a volume source are now deleted if the solver spacing is changed.
• Fixed an issue that would delete the resource file of a “Statistic” resource object along with simulated and post-processed data when the user performs a “Delete data” action.
• Fixed possible crash during scene loading when using the force sensor in a scene with no-gap enabled.
• Fixed crash that occurred when deleting a solid while picking a particle of this solid.
• For dynamic solids, there is now an additional property allowing to manually specify the objects volume instead of using the automatically calculated one. This fixes the issue that a changed volume was overwritten when loading a scene.
• Fixed issue that memory consumptions reported for Solids was wrong when using the RBPS.
• Fixed issue that in very rare cases, a mesh was not sampled correctly with boundary particles.
• Fixed an issue that sensor planes and force sensors did not clear the displayed values immediately when executing Delete simulation data in the timeline and ‘update sensors at substeps’ is disabled.
• Improved numerical precision of the RBPS solver.
• Fixed an issue that the OSD of an airflow object does not get hidden as soon as “show sample points” is disabled.

Optimized

• Optimized Preon Solver performance by up to 20% for scenes with deep water / fluid.
• Reduced loading times of large STL files.
• Improved MPI performance in scene with sparse fluid or few particles.
• Saving an untitled scene on the same partition or file system does not involve making many copy operations anymore, but simply renames the cache directory. Before, this was only done when saving into the “PreonScenes” directory.
• Fixed issue that the RBPS could consume more memory than necessary in some cases.
• Significantly reduced memory consumption required by the dynamic sampling system. This can be relevant in scenes with very detailed meshes or in scenes with a very high amount of solid objects.

Removed

• Removed the compress option from the “Save As” dialog, since compression is usually already applied when simulating and double compression may cause problems.
• The deprecated access to the current loaded scene via preonpy.scene is removed. Use preonpy.current_scene instead.
• It is not possible anymore to create an Area source with a predefined area type property by calling scene.create_object with "Square source", "Circle source", "Flat jet source" or "Rain source". Use scene.create_object("Area source") instead and set the area type property manually.
• Passing simulation start and end as frame numbers to PreonCLI/PreonNode without specifying the --frames is not possible anymore. Consider using the time format, e.g. 0ms 100ms, or add the --frames argument.

[3.3.4] - 2019-08-12

Fixed

• Fixed an issue that the force sensor always computed zero friction in non-MPI mode when post-processing a scene that had been closed and reopened after simulating.
• Fixed issue when using dynamic sampling in an MPI simulation on one of the integrated solid shapes offered by PreonLab (like Plane and Box).
• The rain source now uses the same pseudo-random generator algorithm across all platforms.

[3.3.3] - 2019-06-26

Fixed

• Fixed an issue when applying the wading script to scenes with specific transform hierarchies that surround the car suspension model.

[3.3.2] - 2019-06-21

Fixed

• Fixed MPI synchronization issue / crash related to thermodynamics.
• Fixed issue that the tangential velocity reported by the sensor plane and sensor mesh was incorrect in some cases.
• Fixed possible crash that could occur in some circumstances after removing a force sensor that was connected to a solid.
• Fixed a bug in the viscosity computation that led to wrong results in the bulk viscosity when changing the spacing of a fluid after loading the scene.

[3.3.1] - 2019-06-05

Fixed

Solver:

• Fixed an issue where setting an isothermal temperature in the fluid solver is not reflected in the temperature-based particle coloring.

PreonCLI:

• Fixed a potential abort related to supported characters in the terminal environment.

Miscellaneous:

• Fixed an issue in the legacy loading of scenes created with a car suspension model and a PreonLab version smaller than 3.3.0.
• Fixed issue that a volume source with hexagonal filling could generate particles below its valid volume.
• Fixed force sensor crash when changing the fluid spacing while using dynamic sampling and no gap boundary handling.
• Fixed a bug for heat-flux-based coloring of solids in cases where the property ignore dry areas is set to on.
• Fixed a bug which prevented the serialization of heat flux and heat transfer coefficient for solid objects.
• Fixed a crash in MPI simulations for scene setups that have the, currently unsupported, heat transfer coefficient computation enabled.

Optimized

• Improved the performance in scenes with thermally interacting solids and fluids in which heat transfer computation is disabled.

[3.3.0] - 2019-04-23

Added

Solver:

• Added power-law viscosity model.
• Added an option to get resolution-independent friction forces at the fluid-solid interface. Resolution-independency is guaranteed for a roughness of 1.
• Added an option to get resolution-independent thermal diffusion at the fluid-solid interface. Resolution-independency is guaranteed if the fluid conductivity equals the conductivity of the solid.
• Added an option to compute the arithmetically averaged conductivity at the interface of the fluid as an alternative to the product averaging proposed by Monaghan.
• Added Preon solver (Preview settings) to the add menu which will insert a Preon solver with preconfigured settings that will become the new defaults in PreonLab 4.0.

Solids:

• Added dynamic sampling property to most solids. If activated, the solids will only generate boundary particles where they are required. By default, this is set to off for PreonLab 3.3, but will be the default in an upcoming version.
• Added option ignore in rigid body simulation to solids. Solids with this property will be considered by the fluid, but not by the rigid body dynamics simulation.
• For solid objects, added the property ignore dry areas. When this property is enabled only the wet areas are taken into account when computing min, max and average statistics for heat flux and heat transfer coefficient of this solid.
• Solids now also plot their euler angles as statistics.

preonpy:

• It is now possible to get the name, the type and the category of an object.
• Added limited preset support in preonpy. Currently only the solver presets default_physics_settings and preview_physics_settings are available.
• When executing scripts via PreonCLI or the PreonLab Console, the __file__ variable is now set to the file path executed Python script.

Licenses:

• It is now possible to select node-locked licenses in the license information dialog.
• It is now possible to specify if only node-locked licenses, only floating licenses or both types should be checked out in PreonCLI/PreonNode via cli arguments and in preonpy via preonpy.checkout_license.
• Added the --licenseList option to PreonCLI and PreonNode, to print all available licenses.
• It is now possible to checkout simulation thread licenses by pressing enter after specifying the number of threads in the license information dialog.
• If the last used license could not be checked out, a message box is displayed.

Miscellaneous:

• Car suspension model: The center of mass of a car can now be specified via the weight distribution and the center-of-mass height above the wheelbase.
• There is now an experimental features toggle in the user preferences. E.g., the snow solver and gradient correction of the PreonSolver are only shown if this is enabled.
• When performing “save as”, it is now possible to also deselect objects with less than 1MB of data.
• When opening the connection editor for the first time after scene load or scene creation, all objects are centered.
• Added memory consumption statistic for each object of the scene.
• Added memory consumption dialog accessible using Help->Memory Consumption. Removed right-click action Memory consumption of scene instead.
• Static and transient airflows can now be imported via the Ensight Gold format.
• Added new property Statistics Recording->store statistics per substep which allows to define if the statistics of an object are gathered at every simulation step or only at full frames. By default, this is set to on except for rigids and sources. The behavior of sensors may be overwritten by the scene property General->update sensors at substeps.

Changed

Solver:

• Pressure mirroring is now always enabled and cannot be disabled anymore.
• The Morris and Monaghan viscosity models are now combined into a single “Newtonian” viscosity model that has distinct properties for shear and bulk coefficients. Shear viscosity is computed with the Morris model, while bulk viscosity is computed with the Monaghan model.
• For the Preon solver (Preview Settings), the bulk viscosity is per default set to 3 mPa*s, which is three times the dynamic shear viscosity. This is the proposed value for water according to the literature, e.g., “Experimental measurement of bulk viscosity of water based on stimulated Brillouin scattering” by He et al., published 2012 in Optics Communications, Elsevier.
• Removed the PreonViscosity model. It is replaced by the Newtonian viscosity model. Old scenes using the “PreonViscosity” model are automatically adjusted so that the fluid behavior is the same for the given fluid spacing.
• Introduced legacy viscosity values property. It is automatically enabled when loading scenes which were set up with previous versions to enforces PreonLab to compute comparable results. It is also enabled when adding the standard Preon solver via the add menu. For the Preon solver (Preview Settings), this property is disabled.

Sensors:

• Added surface area statistics to the wetting sensor that state the wet area in square meters.
• The percentage wetting statistics now show the wettage in relation to the total mesh area which only works if the mesh area does not contain duplicated triangles. The new surface area statistics should be preferred if possible.
• Renamed Max wetting time statistic into Saturated wettage.
• The file format for wetting sensors has changed and old wetmaps can’t be loaded in PreonLab 3.3. To get accumulated wetting and wetting times back, you need to post-process the scene once again.
• Experimental: Added property track max pressure to the force sensor. For each solid particle, this will store the maximum pressure over time. The gathered data can be used for coloring and it can be exported via CSV.

Sources:

• When using the hexagonal fill mode of the volume source, the gravity direction does not influence the particle alignment anymore. If necesssary, the alignment can now be influenced by rotating the source.

Miscellaneous:

• Porous rigid: On creation, its properties are not modified according to the up axis anymore. Furthermore, roughness and adhesion of the porous rigid are set to zero by default.
• Printing a more informative error message in case the simulation was aborted due to an impractically small timestep.
• The object selection dialog during a save as operation is now always displayed and the available entries are deselected by default.
• Rigid particle samplings are now written to disk the moment they are generated and not when the scene is saved. It is still necessary to save the scene after the simulation to ensure that scene file and cached particle files are consistent.
• preonpy.get_license now also returns the license model of the used main license.
• The meshes of a Preon mesher are no longer kept in memory and displayed whenever the current frame is changed and the behavior is inactive.
• File dialogs filter according to all valid files types at once.
• When exporting a video, it is now possible to include frame 0 in it. This had been disabled previously, as old versions of avconv could not handle it. When experiencing issues, you should upgrade to the newest version of ffmpeg.
• Airflow: The velocities shown when enabling show sample points of an air flow are no longer the velocities from the imported file but are instead interpolated from the constructed velocity grid.
• Removed the possibility to start PreonLab right from within the installer or maintenance tool on Windows. This ran PreonLab in Administrator mode which resulted in problems with Drag & Drop.
• Car Suspension Model: The user can now provide spring constants and damping coefficients for an improved suspension characteristic and damper characteristic, respectively. The allowed deflection is split up into maximum possible compression and maximum possible expansion relative to the static deflection.
• The rigid body solver now stores and loads its gathered statistics. Its respective plot dialog can be accessed via the rigid body settings dialog.

Optimized

• Improved performance and reduced memory consumption for the rigid body particle solver.
• Reduced memory consumption when using two-way coupling.
• The collider does not generate any .prstate files anymore during the simulation.
• Optimized CPU utilization in scenes with many moving solids.

Fixed

Miscellaneous:

• Porous rigid: Fixed a bug where a scaling along the channel axis that is not in line with the spacing could cause a major change in the actual porosity of a porous rigid.
• When loading a scene containing keyframes for legacy properties, i.e., for properties whose name or range has changed in newer versions of PreonLab, the keyframes are now converted accordingly.
• Preon Mesher now also names the file according to the model frame if the mesh is created via the GUI interaction (“Save mesh”, “Mesh sequence”).
• Fixed issue that the RBPS did not work correctly when a scene without a Preon Solver was loaded and a Preon Solver was inserted subsequently.
• If you deselect an object before a save as operation, the statistics are also not copied.
• Fixed exception being thrown when a single particle tracker is connected to a rigid particle.
• It is not possible anymore to save the scene while simulating. This could have lead to undefined behavior.
• Fixed issue that enabling “override color” in a texture material ignored the texture.
• Fixed issue in the plot dialog where, for small values, the position marker would not be projected onto the nearest sequence curve correctly.
• Added additional safety checks to detect invalid (not-a-number) timesteps. In these cases, the simulation will be aborted.
• Fixed issue that the summed volume of a sensor plane or sensor mesh with keyframed behavior was sometimes incorrect when simulating or post-processing multiple times.
• Added unit to global velocity shown when rotating a drag force. Also added unit to drag force property tooltips.
• Added missing icons in some dialogs on some Linux desktop environments (e.g. KDE).
• Fixed a bug in the Plots dialog with smoothing enabled, where the smoothing width was set to smaller-than-needed number when the user entered a number that was larger than the maximum allowed width.
• Fixed an issue that sensor planes and force sensors did not clear the displayed values immediately when executing Delete simulation data in the timeline.
• Fixed a potential crash that could occur when deleting an object that is contained in a group in the connection editor.
• Fixed a rare crash that could occur when too many update requests are sent to the progress dialog in a very short time.
• Fixed an issue that in rare occasions applying a material preset did not change all of the properties the preset contains.
• The path to resources outside of the scene directory, that are referenced with a relative path, is now kept intact when saving a scene to another location.
• Fixed issue that the frame loader did sometimes not recover from a previous frame loading error.
• Fixed an issue in the velocity computation for guided solids.
• The action ‘Export state as CSV’ for Solid objects now includes the global positioning of the sample points.
• Fixed functionality of scene property update sensors at substeps.
• Simulation and post-processing performance is no longer affected by invisible air flows which have the show sample points property enabled.
• Fixed font issue when rendering a color legend on a transparent background with Preon Renderer.
• Fixed the issue that the current value of the temperature property of solid objects has not been considered for the simulation when jumping to a different frame after setting the temperature.

Alembic:

• Fixed that Alembic debug libraries are shipped on Linux.
• Fixed that an Alembic mesh with load transformation samples set to off displayed velocities for rigid particles anyway when VelocityBased coloring was activated.
• Fixed issue that an Alembic rigid which has both load transformation samples and load mesh samples set to off showing an infinite yellow cache marker range in the timeline.
• Fixed issue that an Alembic rigid that has an animation time factor other than 1 has wrong particles velocities.
• Fixed issue that scene background image and OpenGL recording resolution was not saved to the .prscene file.

preonpy:

• It is now possible to save a scene in place while using the subsample or compression feature.
• Fixed an issue in preonpy where the function ‘get_connected_objects’ would return an empty list in case the slot label differs from the slot name.

MPI:

• The outflow domain can now be used in MPI simulations.
• Domains now report correct statistics (deleted and scripted particles) in MPI mode.
• Fixed crash / timeout issue when using an active force or wetting sensor connected to an inactive solid.

[3.2.3] - 2019-03-06

Fixed

• Fixed issue that fast moving area sources failed to emit fluid continuously in rare cases.
• Fixed an issue for airflow imports with more than 179 million sample points.
• Fixed an issue for smoothed statistics in the plot dialog.
• Fixed an issue that could lead to negative pressures in postprocessing in rare cases.

[3.2.2] - 2019-01-09

Fixed

• Fixed issue that using an invisible sensor mesh could lead to undefined behavior.
• Fixed an issue in the airflow import process with respect to position scaling and velocity scaling.

PreonPy:

• When using spline interpolation, it is now possible to directly set the keyframe gotten from an object or property to another object or property. Previously, the interpolation type of the last keyframe in the sequence had to be modified manually.

[3.2.1] - 2018-12-11

Changed

• Removed “Export Frame” functionality which was not intended to be exposed.
• Expanded PreonNode MPI debug logging functionality.

Fixed

• Fixed an issue with the Monaghan viscosity model that led to a crash in very rare occasions.
• Fixed an issue where temperatures mapped onto a solid would occasionally not be loaded correctly on re-opening a saved and closed scene.
• Fixed very rare crash that could occur when trying to load a scene while simulating.

[3.2.0] - 2018-11-20

Added

Solver:

• Added an implicit solver for the viscosity force, which largely improves the performance when simulating higly viscous fluids.
• Added new Monaghan viscosity model, which is particularly suitable for highly viscous fluids.
• When the viscosity varies spatially due to multiple phases or due to temperate-based viscosity, the viscosity forces are now computed in a symmetric way. This improves momentum preservation in these scenarios.

Sources:

• It is now possible to emit rain from a Flat jet source or Area source using the new, more powerful Area source (see Changed section for more details).
• Added cone emit area type to the new Area source.

Thermodynamics:

• Added possibility to colorize a rigid based on the heat transfer to other participating media (i.e. air, other rigids, fluids).

Miscellaneous:

• Added new spline-based interpolation method for keyframing. This is the new default for new keyframe sequences and allows you to define smooth sequences with less keyframes than before.
• The video export dialog now automatically guesses the FFmpeg file if the location containing the binary is included in the PATH environment variable.
• When trying to import an unsupported file with drag & drop, an error message is shown.
• Added ability to colorize pahtlines via particle temperature.
• Added hotkey (Ctrl + G) to take a screenshot of the currently active OpenGL viewport.
• Added cylinder shape to outflow domain.
• A single outflow domain can now be connected to multiple sources.
• Added preonpy interface for ensight export.
• Improved help text for PreonCLI and PreonNode.
• PreonNode and PreonCLI now accept start and end arguments in time format.
• PreonNode now writes if an message is only a warning or an simulation-aborting error.
• Improved performance of CSV export of pathlines and added a progress bar with the possibility to cancel the export.

PreonPy:

• Added Python bindings to get and set keyframes with ‘Spline’ as interpolation type.
• Added Python bindings for the export of rigid particle transient data, e.g., heat flux and heat transfer coefficient, to the CSV format as well as the ensight format.
• Added Python bindings for the export of fluid particle transient data, e.g., velocity and pressure, to the CSV format.

Optimized

• Solids are now only sampled with particles when it is required (typically by the simulation). This greatly reduces memory consumption and improves performance when opening scenes for post-processing.
• Greatly reduced memory consumption of Preon Solver during post-processing.
• Added “rendered particles target” to the user preferences. This sets the target number of rendered particles (in million) per fluid solver object. If necessary, particles will be downsampled to a coarser resolution to match the target. This greatly improves performance and stability when post-processing scenes with very high particle counts using the graphical user interface.
• Optimized loading of compressed .prstate files, which can speed up post-processing by up to 30%.
• Improved impact of GL rendering performance in some scenes with few particles.
• Improved frame loading performance for Alembic rigids if load mesh samples is off.
• Slightly improved Preon Renderer performance for scenes with triangles that vary in size.
• The air flow visualizer does not update itself unnecessarily anymore during simulation or post-processing.

Changed

Sources:

• Merged Area source, Square source, Circle source, Flat jet source and Rain source into one. This combined source is called Area source and supports all features offered by the old sources.
• The new Area source does not store or load per-frame .prsim files anymore.
• Source statistics are now only updated and serialized per frame to save memory.

OSD:

• The width of the dropdown list for selecting a camera is now adaptively adjusted depending on the camera names, preventing cropping of names.
• Fixed an issue that letters with parts below the baseline were cropped.
• Added property “show color legend” that enables to always show or hide the color legend, or to display it when data is availabe. This is beneficial when exporting to a video, where it may be distracting when the legend appears and disappears from frame to frame.
• The color legend is now hidden if the corresponding object is set to “invisible”.
• The unit of a color legend is now only shown once in the title and not for each value that is displayed.
• When using a marker in the color legend of a sensor plane, it does not overlap the color legend title anymore.

Rigid body:

• Bullet specific properties are no longer shown in the property editor if Particle-based rigid body solver is used.
• Exposed Bullet specific properties: rolling friction and collision margin.
• An exception is now thrown if it is tried to simulate rigid body dynamics with the particle-based rigid body solver without having at least one fluid in the scene.

Rendering:

• The “override color” material property now also overrides object opacities with the alpha component of the specified material color.
• The specular term of the Surface material is not influenced anymore by the opacity (in Preon Renderer).
• Replaced the “glass transparency” property of the Surface material with the new “glass reflection” property. This change allows to realize less transparent and / or colored glass.
• Added property “exclude from reflections” to all objects (in the “Appearance” group). If this is enabled, the object will not be mirrored in reflective surfaces. This is mostly intended for sensors.

Preon solver:

• Artificial viscosity is not enabled per default and no longer recommended.
• Thermodynamics: The properties ‘heat capacity’ and ‘thermal conductivity’ are keyframable now in all thermal objects (fluid solver, solids, air objects).
• Thermodynamics: The property ‘temperature’ of a solid will now be hidden as soon as a temperature field is connected via the ‘TemperatureSamples’ slot.
• Evaporation: The surface detection as well as the surface area estimation has been improved leading to a more robust evaporation process and reduced calibration time (w.r.t. prefactor).
• Improved handling of fluid evaporation between free-surface particle layers.
• In the property editor, properties related to viscosity, cohesion and adhesion are now grouped to give the editor a clearer representation.

Miscellaneous:

• At least one of the properties have to be selected in the respective export dialog before being able to “Export sample data to CSV”.
• Removed option to disable tracking and recording of statistics for all sensors since the purpose of sensors is to measure and store statistic values.
• In PreonNode the --testThreads command now takes precedence over the simulation.
• If you pass start and end frame to PreonNode and PreonCLI you will now get a deprecation warning. Consider passing --frames or using times.
• The OSD of point cloud resources now consistently displays all velocities in m/s. Previously, the length unit depended on the data of the point cloud.
• The OSD of point cloud resources is now also shown when simulating a scene that was loaded from disk. Previously, the OSD had not been shown in this case.
• Evaporation solvers (for fluids) and rigids with wetting films now report the simulation time from where no more evporation is possible. Either there is no mass left to evaporate, or no free surface could be detected.
• When using velocity or acceleration as position or orientation control mode, the resulting position / orientation profile is now integrated analytically which improves accuracy and memory usage. The “integration timestep” property is removed because it is not needed anymore.
• Ctrl+K now creates a transformation keyframe with spline interpolation unless spline interpolation was explicitly disabled for the sequence. Removed Ctrl+L shortcut that previously created a transformation keyframe with linear interpolation.
• The post-processing dialog for per-sample data sensor export and rendering now shows whether the respective cache directories contain files from previous exports in the form of a time interval. If the time interval overlaps with the interval of the new export/rendering, data will be overwritten. If the export/rendering is canceled, files already written are not deleted anymore.
• Removed cancel button for scene loading operations.
• Replaced the “Purchase desktop license” button with sales contact information.
• When passing deprecated object types Square source, Circle source, Flat jet source or Rain source to the preonpy create_object method, the corresponding area type and emit type are set and a deprecation warning is printed. Starting with version 4.0 this will not be possible anymore.

Alembic

• Alembic files with HDF5 backend can no longer be loaded or saved with PreonLab. Instead, the Ogawa backend is now used. This means that if you want to open Alembic files with the HDF5 backend in PreonLab you first need to convert them to use the new Ogawa backend. This can be done with the command-line tool we provide on the download page.
• Removed non-hotloading Alembic import. Importing an Alembic file now always creates an Alembic rigid.
• Alembic rigids can be used in MPI simulations when load mesh samples is off. Otherwise an aborting error is thrown.
• Alembic rigid now set the load mesh samples property automatically depending on if multiple mesh samples are found in the Alembic file.
• PreonLab now not only checks if normals are existing in an imported Alembic mesh but also if they are non-zero. Else, they are recomputed by PreonLab.

Fixed

Solver:

• Changing the dimension is now automatically synchronized when there are multiple solvers in the scene.

Sources:

• Fixed emission issue for copy and pasted continuous sources (like Circle sources).

Rigid body:

• Fixed that adhesion forces did not contribute correctly to two-way coupling.
• Fixed being able to change the rigid body solver during simulation, which led to a crash previously.

MPI:

• Fixed a statistic / frame saving issue when using a view frame rate that differs from the simulation frame rate.

Miscellaneous:

• Fixed a problem in the plot dialog that would display NaN as the average of statistic.
• Trash folders are never copied anymore when saving a scene to a different location.
• Fixed that on Linux the text in the License server dialog was cropped.
• The spacing of rigid objects can now be smaller than 1e-6.
• Fixed an issue where the evaporation solver would switch to a ‘framewise’ equilibration phase although a full frame has not yet been reached.
• Prevented a crash for some setups that required too much memory. PreonLab will now show an error instead.
• Fixed issue that particle picking did not work on Solids when using a material with override color enabled.
• Fixed issue that when loading a scene, connection editor did not show the whole space in some cases.
• Better error message when having no licenses installed and no license server configured.
• There are now tooltips for context menus of the scene inspector.
• Better tooltips and error messages for Preon mesher.
• Fixed issue that the “use scene background” property of Preon Renderer was not correctly loaded from disk.
• Fixed crash when deleting a fluid or solid while using particle picking on it.

[3.1.2] - 2018-09-27

Added

• Added command line option “debugLogging” to PreonNode that can help to investigate MPI related technical issues.

Changed

• PreonNode and PreonCLI now abort the simulation in case a mesh file can not be loaded or a particle sampling can not be generated.
• Improved error logging in some cases in which std::bad_alloc was thrown due to insufficient memory.

Fixed

• Fixed a bug that the maximum value of simulation thread licenses was not correct in some cases.
• Fixed a bug that could prevent multiple simulation thread licenses from being checked out.
• Added more informative error messages in case the license check fails for PreonNode, PreonCli or preonpy.
• Fixed ensight export with a start frame larger than 9.
• Fixed a crash that could occur when enabling RigidNeighborhoodBased coloring.
• Fixed MPI synchronization issue that could occur with some MPI implementations in scenes with a very high number of fluid or solid particles.
• Fixed issue that the “Total Solid Particles” and “Active Solid Particles” statistics were incorrect for scenes with more than 2 billion solid particles. Please note that each individual Solid is still limited to 2 billion particles.
• Fixed formatting of log error and warning messages.

[3.1.1] - 2018-09-11

Fixed:

• Fixed a bug that prevented licenses from being checked out, if multiple licenses for the same product are available.
• Fixed issue that in some cases, there was no error message when the particle limit specified by sources or solids was exceeded.
• Fixed different behavior of flat jet source when connected or not connected to Transform parent.
• Fixed issue for flat jet source for very slow emission speeds.
• Fixed issue that the rigid boundary sampling was not correctly synchronized in mpi simulations in some cases. This could lead to undefined behavior when using the Preon Solver option “mirror pressure off”.
• Added more informative error messages in case the license check fails for PreonNode, PreonCli and preonpy.
• Fixed mpi synchronization issue that could occur at very high particle counts.

[3.1.0] - 2018-08-06

Added

Solver:

• Added Morris viscosity model, which is also the new default model.
• Added option “stable initialization” which discards velocity changes due to pressure for particles in their first simulation step. This option is enabled by default for new solvers, but disabled when loading old scene files.
• Added option to clamp particle pressure values or delete particles above a pressure value that can not be represented accurately by PreonLab. This prevents a timestep of zero in rare cases.
• Added right-click action to export fluid particles of a solver as a .csv file.
• Ouflow domain: Added new control conditions velocity and continuative. For velocity, min and max target speeds can be defined which are applied to outflow particles if their speed is not in the given interval. The continuative condition keeps the velocity of particles unchanged. For velocity and continuative condition, particles are deleted if their velocity deviates significantly from the outflow direction.

Rigid body:

• Added experimental particle-based rigid body solver. You can switch between Bullet and the new rigid body solver using the Settings->Rigid body settings menu.

Renderering:

• The Surface material (previously Phong material) now supports reflections which allows to render surfaces like metal realistically.
• Added option to Surface material to render thin, two-dimensional glass.
• Added a path-tracing mode to Preon Renderer that supports soft shadows and rough reflections. Enable the “monte carlo light transport” property in a Surface material to use path tracing for this material.
• An artificial hemisphere is now used by default for rendering water or solid reflections. You can disable this for Preon Renderer using the new property “artificial secondary hemisphere”.
• The properties “override color” and “color” are now also available for the Volumetric material (previously Water material).
• Added various material presets for the Surface and the Volumetric material. The presets can be applied via right-click actions.
• You can now right-click on one or multiple selected solids or fluids and connect an existing or a new material to them.
• Added possibility to use a transparent background in Preon Renderer.
• Preon Renderer now applies a dithering pattern to the background to avoid color banding. You can weight the dithering amount using the new “background dithering” property.

MPI:

• MPI now supports thermodynamics for fluid-fluid interactions and for fluid-solid interactions where the solid acts as a specified boundary condition.
• Added network benchmark to PreonNode that is performed at startup and reports the transfer speed from node 0 to all other nodes.

Miscellaneous:

• Multiple statistics files can now be imported at once via Import Statistics.
• Added import dialog “Import Velocity Field” to intialize a Point cloud resource from a CSV file.
• Added presets for solver particle coloring, scene background and camera configurations. The presets are applied via right-click actions.
• Added right-click action to export pathline data as a .csv file.
• Added a tooltip for the right-click action “save cell status in image” of sensor plane.

Changed

Solver:

• Particle data that was loaded from disk and is not explicitly marked for serialization is now not serialized anymore when writing .prstate frame files.
• Changed the default viscosity model from PreonViscosity to Morris. Removed the Laminar_Morris model.

Sources:

• It is now possible to specify the initial velocities of particles emitted by a volume source using the new “VelocityField” input slot. As velocity field output, you can either use a moving / rotating rigid or a Point cloud resource with velocity CSV samples.
• Removed the spacing property for all sources.

Rendering:

• Renamed “Phong material” to “Surface material”.
• Renamed “Water material” to “Volumetric material”.
• The Volumetric material can now be applied to Solids to render volumetric glass.
• You can now specify the index of refraction in the Volumetric material.
• Adapted Surface material parameters, please see the manual or tooltips for further information.
• A light source that casts shadows now overrides “two sided lighting” for all materials.
• Removed the possibility to connect a hemisphere material to Preon Renderer.
• Removed obsolete attenuation properties from the Point light.
• The Rendering dialog does not clear the existing image when rendering anymore, but instead paints the new over the old one.
• The background colors are now properties of the Scene and not the Scene UI Settings. By default, Preon Renderer will now use this background. To specify a separate background in Preon Renderer, you need to disable the new “use scene background” property.
• Removed the material input slot for the mesh resource. Materials are now always specified per solid object.
• The specular lighting term in the surface and volumetric material is now energy-conserving. This eliminates the need to tweak the specular lighting factor in many cases. For the volumetric material, the specular lighting factor is reset if you load an old scene.

Evaporation:

• If thermodynamic simulation has been performed before enabling the evaporation process, the per-particle temperatures of the fluid can be employed as input for the evaporation process.
• The windspeed prefactor of the evaporation coefficient is now a property of the evaporation solver.
• You can now specify the thickness of the fluid layer at the air interface that can be evaporated within the current simulation step w.r.t. particle mass. If greater than 1, more than one layer of particles could be evaporated at once (default is 1).

Thermodynamics:

• The diffusion model has been adapted. It is now resolution-independent for fluid-fluid, fluid-rigid, and fluid-air interaction. The diffusion model for solid objects is still experimental.
• The temperature checkbox is now disabled when exporting sensor plane / sensor mesh data as csv and no thermodynamics have been computed.

preonpy:

• Installation of the preonpy .whl file now also automatically installs its dependencies.
• You can now provide different input and output slot names to the connect_objects method.
• Added get_connection_slots method that returns a list of connection slots together with connected nodes.

Miscellaneous:

• The timeline now has a crop before and crop after right-click actions that are more consistent with the delete all action and no longer change the scene.
• The freeze movement properties for dynamic objects is now keyframeable.
• You can now specify a animation time factor for Alembic objects to playback an animation faster or slower.
• Updated RLM library: Optimized license checkout procedure.
• Updated the tooltips of all objects in the add menu to be more descriptive.
• Changed the name of the dialog “Import Point Cloud” to “Import Temperatures” in order to differentiate it from the new “Import Velocity Field” dialog.
• Right-clicking in the graphics window now shows a context menu if there is a selected object.
• Improved the error logging when saving and a filesystem related error occurs.
• The scene inspector now also shows the invisibility icon for objects with an opacity of 0.
• The input field for time in the plot dialog are using the time format now.
• The time value printed in keyframe editor for the current mouse position is now using the time format.
• CSV export of multiple keyframes from temperature to value is now supported.
• Mesh import: File name is now printed if no mesh is found in the imported file.
• PreonCLI and PreonNode now consider the OMP_NUM_THREADS environment variable.
• When exporting statistics as CSV, the time column now has the name “time” (previously “Time”).

MPI:

• Renamed the “noMachineCheck” startup option to “noPerformanceChecks”.

Optimized

• Improved performance in long simulations that produce new frames quicky, typically raining simulations.
• Fixed issue that photon mapping impacted the rendering performance in scenes without any fluid particles.

Fixed

MPI:

• Fixed rare issue that solid particle samplings could not be synchronized during scene loading.
• Fixed issue that resuming an existing simulation did sometimes not work correctly.
• Fixed a rare crash, that sometimes could occur when using high node counts.

Rendering:

• Fixed issue that transparent surfaces did not cast correct shadows in Preon Renderer.
• Fixed rendering artifacts for objects that are not located near the position (0,0,0).
• Fixed issue that color legend text was sometimes not rendered correctly by Preon Renderer.
• Fixed Preon Renderer issue when a transparent and non-transparent surface was located at the same position.

Miscellaneous:

• Fixed the loading and saving of empty rigid samplings from HDD.
• Fixed that newly pasted objects (via CTRL+V) were not directly marked as selected in the connection editor.
• The bounding box of a point cloud resource becomes invisible after changes to its input parameters or its transformation.
• Fixed an issue that start and end time markers in the timeline were set wrongly when undoing frame rate keyframes.
• Updated RLM library: License server broadcasting now works on linux too.
• Fixed issue that the “Recompute normal vectors” right-click action did not work if the Solid was connected to a mesh resource.
• Fixed issue that Solids were not correctly resampled when switching the action of a connected boundary domain from “deleteFluidParticles” to “deleteAll” or “deleteRigidParticles”.
• Fixed that force sensor did not colorize the connected rigid if the pressure, adhesion and friction force display properties were off and the pressure display property was on.
• Fixed a problem that could cause data loss when saving an untitled scene in combination with a filesystem related error.
• Fixed very rare issue that Mesh_Independent sampling generated incomplete particle samplings for some geometries.
• Fixed being able to generate particles for a mesh via right-click during simulation which would then stop the running simulation. Now, a warning is shown that the simulation first needs to be paused.
• Fixed problems when saving a scene with dots in its name.
• Importing keyframes now immediately updates the graphics window and creates an undo event.
• Fixed issue that undo and redo did not work correctly when overwriting keyframes using the key pasting functionality.
• Mesh import: Files with dots in the filename no longer result in objects in PreonLab with dots in the name which are invalid names.
• Fixed that air flow objects created by the import airflow dialog were not directly selected after creation.
• Fixed that the message count for info messages was not increased correctly.
• Crop-before and crop-after actions now consider simulation data of rigids and sensors.
• Increased numerical precision when keyframing eulerAngles or when using the orientation control modes revolution or revolutions per second, which can improve solver accuracy in long simulations.
• Fixed issue in copy&paste of objects where connection partners would not be found.
• Fixed issue in copy&paste of objects where transform connections would not keep the relative positioning to connections partners.
• Fixed issue where the option ‘keep every x-th frame’ on saving the scene did not take effect for specific objects (e.g. wetting sensor).
• Fixed issue that sensor mesh was sometimes not colored correctly when nothing was measured.
• Fixed issue that Point Cloud Resources did not use their color for rendering the sample box.
• Fixed issue that the sensor plane and sensor mesh did not export the positions of samples without measured data correctly.
• Fixed issue that sometimes undo/redo did not work correctly when modifying existing keyframes using the keyframe editor.
• Fixed issue that the timeline cache marker did not work for velocity projection fields and height fields.
• Fixed issue that it was possible to connect multiple mesh resources to a single rigid.
• Fixed issue that the OSD sometimes displayed an inaccurate elapsed time when simulating without any solver in the scene.
• Fixed issue that it was possible to create frame rate keys with a linear curve type using the property editor.
• Fixed an issue in the evaporation solver that prevented to properly continue the simulation of an ongoing evaporation process after saving and reloading a scene.
• Switched compression method for evaporation solver data to lossless.

[3.0.5] - 2018-07-06

Fixed

• Fixed issue that rotating solids could lead to a timestep that was smaller than required. This might significantly reduce the computation time of gear simulations.

[3.0.4] - 2018-07-04

Fixed

• Undeterministic emission of rain source when duplicating a scene with “save as”.

Changed

MPI:

• Before starting the simulation, PreonNode now logs the combined number of threads that will be used in total, considering all worker nodes. Additionally, each worker node will log how many threads it will use locally.
• Added new PreonNode option “–testThreads” that allows you to start PreonNode without specifying a scene file. It will not simulate anything, but just log how many threads and worker nodes would be used in a simulation.
• By default, PreonNode now ignores the scene property “individual threads” and always uses the maximum number of available threads per node. You can pass the “–allowSceneSpecificThreads” option to restore the old behavior.
• Unless –noMachineCheck is specified, PreonNode will now check whether all processes use at least 4 threads and will refuse startup otherwise. A low thread count per worker is usually a sign of an incorrect configuration.

[3.0.3] - 2018-06-21

Fixed

• Fixed very rare crash that could occur in MPI simulations with mirror pressure off.
• Fixed issue that in mpi mode, .prstate fluid files were sometimes skipped when using a lower view frame rate than simulation frame rate.

Sensors:

• Made sensor plane and sensor mesh numerically more robust. This fixes a rare issue in which the sensor plane measures “not a number” values for very high resolutions.

[3.0.2] - 2018-05-30

Changed

• PreonNode now checks if all participating nodes run the same program version and refuses to start if they don’t.
• PreonNode, PreonCLI and preonpy now start simulating and/or postprocessing with the previous frame and end with the next frame if the start and/or end time do not exactly match a frame.
• Removed internal statistics from the deployed version of PreonLab.
• The “Saving” timing of the scene is now consistent with the “Postprocess” timing in that it is updated every simulation substep.
• Improved error / info messages in case .prsampling files can not be loaded in MPI simulations.

Fixed

• Fixed rare crash in connection editor when grouping an already existing group.
• Fixed number of fluid particles statistics in MPI mode.
• Fixed issue in the plot dialog that auto-zoom did not work sometimes.
• Fixed that dynamic rigid bodies did not get a rotation from two-way coupling forces if the respective movement axis were frozen.
• Fixed numerical precision issues in Preon Renderer when using a camera with a high far clip distance.
• Fixed issue that color gradient backgrounds were sometimes not rendered correctly in Preon Renderer.
• Fixed issue that the warning “Unable to achieve volume flow rate because number of emitted particles is zero!” was emitted for area sources during scene loading for no reason.
• Fixed wrong summed volume statistic of Sensor plane and Sensor mesh in multiple cases (e.g., when the behavior was keyframed from inactive to active, when resimulating from the start without removing existing data, when changing the position/orientation during in the middle of the simulation).
• Fixed that PreonNode, PreonCLI and preonpy postprocessed the wrong frame range if a time range was supplied or the time in the scene file was used and the simulation and postprocessing (view) frame rate had different values.
• Fixed the output of the number of used simulation threads in the CLI/preonpy when starting a simulation and not all possible threads are used due to the available license.
• Fixed potential crash, that theoretically could happen when performing license related tasks.
• Fixed Python2.7 compatibility.

[3.0.1] - 2018-05-03

Added

• Added sanity check when starting PreonNode to prevent PreonNode running multiple times on the same machine.

Changed

• The alpha component of the object color is now ignored for particle rendering. Transparency is still possible (as before) using the opacity property.

Fixed

Miscellaneous:

• Fixed that info log messages were not shown on some systems.
• Fixed crash that could occur in some cases when starting post-processing.
• Fixed area source memory leak.
• Fixed crash that could occur when switching mirror pressure in the Preon solver on or off.
• Fixed issue that rotated sensor planes sometimes measured inaccurately.
• Fixed that scenes written with v2.3.2 did not load the simulation end time correctly in newer versions.
• Fixed a typing error in the property name of “EVP computation method” (located in property group “Physics->Evaporation Solver” of a Preon solver object).

preonpy:

• Fixed bug that causes preonpy to create empty directories when using relative paths.

[3.0.0] - 2018-04-10

Added

GUI:

• New scale draggers in “Scale” mode when control key is pressed which allow scaling in one direction only.
• New option to show the bounding box and axial extents of an object under “Appearance”.
• Particle picking mode - Select single fluid and solid particles to print their physical values in the on-screen-display.
• The preonpy simulate, post_process and load_frame methods are now available in the Console in PreonLab.
• Added a ‘Set as active camera’ action to the right-click menu of cameras.
• Added CTRL+b shortcut for toggling between behaviors (active, cache and inactive).
• Added postprocess dialog which allows to change which objects will be postprocessed.
• Added 3-type-coloring to rigids with default colors blue, green and red.
• Added right-click action “auto-colorize”, which randomly colorizes all selected solid objects.

Connection editor:

• Added filtering based on connection type to the connection editor which allows to reduce the number of visible objects and connection types.
• Added button to automatically arrange visible objects.
• For large scenes, the anti-aliasing is now disabled in the connection editor. This may result in “staircase” rendering of edges but should speed up rendering of the connection graph.

Sensors:

• The scene now has a property “update sensors at substeps” which enables or disables sensor updates at simulation substeps. If this is turned off (which is the new default), sensors will only be updated at full frames (according to the view frame rate) during the simulation. This improves performance, but it also might lead to inaccurate post-processing results if the view frame rate is not high enough.
• Added particle tracker which tracks the physical values of a certain fluid particle defined by its ID and shows its trajectory.
• Added new property “TangentialVelocity” for sensor planes and sensor meshes that measures tangential velocities.
• Statistics for height field and velocity projection field.

MPI:

• Added MPI support. Distributed MPI simulations can be launched via the new executable PreonNode.
• Added lightweight MPI implementation wrapper, so that the specific MPI implementation (OpenMpi, MPICH) can be chosen at install time.

Thermodynamics:

• Added computations of thermodynamics between fluid-fluid, fluid-solid and fluid with implicit air phase.
• Added relevant thermodynamic properties like temperature to Preon solver, solid objects, particle sources.
• Added coloring mode for temperatures.
• Added volume sampling of solids in addition to the boundary sampling. The volume sampling is employed for solids which require the computation of the thermodynamics across their volume. (experimental)

Film wetting:

• Added a model to simulate the wetting of solid objects. Fluid particles do now lose fraction of their mass when in contact with solids which have film wetting enabled.
• Added relevant properties for film wetting to solid objects.
• Added visualization mode for film wetting.

Evaporation:

• Added computational model to simulate the evaporation of fluid and film wetting for solid objects.
• Added relevant evaporation properties to Preon solver and solid objects.
• Added an air object that provides boundary conditions for fluid-air interaction w.r.t. thermodynamics and evaporation.

Sources:

• You can now connect a point object to a volume source via the new “Badpoint” slot. If fluid generated from a seedpoint will reach this point, the volume source will not emit particles but instead print an error and visualize the shortest path from the seedpoint to the “Badpoint”. This helps to detect small holes in your geometry that prevent a successful filling.
• “Static source area” is now enabled by default for Area sources because it can greatly improve performance in some scenes. If you need a dynamic source area, please enable the option manually.

PreonCLI/preonpy:

• Added simulate and postprocess methods that require no start and end frame and instead use the information from the scene.
• Simulate and postprocess methods now also take start and stop time instead of frames (format “mo:d:h:m:s:ms”) (preonpy only / PreonCLI still parses frames only).
• Postprocess method allows to specify a whitelist of objects that should be postprocessed.

Licensing:

• New license options for distributed simulations using MPI.
• PrePost can now simulate with 2 threads which allows to verify scene setups.
• Added more options and informations to license dialog. Number of total and free licenses for the current license server are listed. Added options to checkout different license types and to add simulation threads to PrePost license.

Miscellaneous:

• Possibility to apply the scaling of an object to its pivot.
• Car Suspension Model for wading simulations: The deflection of the suspension of a car can be modeled based on the pressure forces exerted on the sprung mass of the car by fluid. The model improves water wading simulations with high car velocities and/or high water levels.
• Added new object “Point cloud resource” which represents spatial data imported from external CSV files.
• Added subgroup “Transform connections” to property group “Transformation”. Its properties define the behavior of an object when added/removed from transform hierarchies and their behavior within such a hierarchy. Therefore, the property “inheritance mode” has been moved to this subgroup as well.

Changed

GUI:

• The message window and the console are now shown in the same area as the property editor as a dedicated tab (per default).
• Reworked the console with more detailed outputs, and to support drag and drop of script files and control over last run scripts.
• Properties that are encoded by a string, e.g. a name, are only changed when the editing finished. This makes renaming objects much easier as they temporarily (while editing) can have the same name as an other object.
• Ordered the menu entries in File->Import and File-Export alphabetically.

Timeline:

• Timeline has now three dedicated modes: Simulate, Playback, Postprocess. The playback mode does not change any statistic data of sensors.
• Single-step is enabled by pressing the control key (defined in User Preferences) when mouse is over mode toggle.
• Timeline supports zooming with the mouse (either pressing middle mouse button and drag or scrolling with the mouse-wheel).
• Start and end times for simulation and playback/postprocess mode can be specified via movable markers in the timeline and via the corresponding scene properties.
• In simulation mode, frames correspond to simulation frame rate, while for post-process and playback, the frames correspond to the view frame rate.
• Changing frame rates does not change the end time.
• Clicking in the timeline does not stop the simulation, postprocess or playback run anymore.

Solver:

• Enabled particle file compression by default for new scenes.

Sources:

• Removed “preview particles” option from the volume source. The preview is now triggered via a right-click action.

Sensors:

• Volume sensor: In addition to measure the volume of fluid particles, now you can specify to measure the volume of rigid particles as well.
• It is now possible again to connect a wetting sensor and a force sensor to the same solid.

Renderering:

• Preon renderer now draws color legends of all objects intstead of just fluids.
• Preon renderer is now active by default (only matters if you connect cameras to it).
• Fixed issue that fluid behind many layers of transparent objects was sometimes invisible.
• Exposed “max. solid recursion depth” and “max. fluid recursion depth” properties to the user.
• Preon renderer now supports the “range exclusively” coloring option for fluids.
• Removed possibility to connect a material to Preon Renderer which controlled the background color. Also removed “fixed background color” property and advanced anti-aliasing properties.

CLI:

• Changed the executable name to PreonCLI.

Miscellaneous:

• You can now specify two background colors instead of one in the UI Settings and in Preon Renderer. The two colors are then used to draw a smooth color gradient across the hemisphere.
• Improved scaling behavior of the scale dragger for very small and big objects.
• Color legends of sensor plane, height field and velocity projection field now show units.
• The color property of the sensor plane now also specifies the color for cells where no values are measured. This also allows it to be set transparent by reducing the alpha value of the color.
• Collider settings are now stored in the scene file.
• In the keyframe editor, the keyframe time can now be entered (and is displayed) in a more readable format (i.e. “mo:d:h:m:s:ms”). Entering a unitless number equals entering a time in seconds.
• Simulation boundary domains now only delete particles of connected Solids.
• Added option “dynamic particle deletion” for Solids. This enables or disables dynamic particle deletion during the simulation based on boundary domains. It is off by default which improves performance in some scenes.
• Removed “cull rigid particles” for Solids. If there are connected boundary domains, this is now done automatically.
• Added title and unit to the color legend in the OSD of the airflow visualizer.

Optimized

• Improved performance in simulations that use a scripting domain (for instance wading simulations).
• Improved performance in simulations with many moving solids.
• Improved performance in scenes that delete solid particles with boundary domains. However, please note that you need to connect boundary domains to Solids manually now.

Fixed

Keyframe Editor:

• Crash when selected object has no keyable properties.
• Statistics of statistic resources are not cleared when starting a simulation or on reset.
• The edit fields for changing keyframe values are now correctly cleared when the keyframe editor is reinitialized (e.g. when using undo/redo on keyframe changes).
• The viewed area is now kept when the keyframe editor is reinitialized (e.g. when using undo/redo on keyframe changes).

Solver

• Fixed issue that enabling particle compression could lead to instabilities when loading a frame and starting the simulation from there. The fix slightly increases disk consumption.
• Fixed minor inconsistency in the computation of the “Fluid Particles” statistic.

Sources

• Fixed rain source emitting particles too far away from each other in some cases when “specify drop size” is off.

Renderering:

• Fixed minor bug in photon mapping lighting.
• Fixed issue that scripted particles were sometimes not rendered correctly when using the solver option “render scripted particles.”
• The renderer dialog now automatically shows the current frame if it was rendered using “Render sequence”.
• Fixed being able to start rendering a sequence while a single frame is rendered which lead to a deadlock.
• Fixed issue that sometimes transparent objects were displayed incorrectly after resizing the window.

preonpy:

• When querying the minimum/maximum value of a statistic sequence, undefined values are not considered in the response.

Miscellaneous:

• Fixed rare issue in triangle mesh BVH construction (used in Volume Source, Area Source, rigid sampling, Sensor Plane and Preon Renderer) that could lead to a stack overflow on windows and poor performance on other platforms.
• Fixed video export misjudging the duration of the ouput video if the user tries to export a subset of the rendered images.
• Fixed an issue with picking if mouse is only moved horizontally or only vertically while mouse button is down.
• Fixed issue that it was possible to connect some incompatible connection slots in the connection editor.
• Fixed an issue in the volume source in cases where a seedpoint is employed and positioned outside the bounding box of the source.
• An air flow object without a given sample data path now just uses the set air velocity everywhere instead of not applying any force.
• Prevented insertion and deletion of objects while the simulation / playback thread was running.
• The sensor mesh color legend is now directly shown/hidden in the osd if the visiblity of the sensor mesh changes.
• Fixed the issue that the warning “AABB outdated” has been shown unjustified.
• A warning message box is now shown if there is no fluid connected when trying to generate pathlines.
• Fixed crash that could occur when simulating after deleting the connection from a solid to a sensor mesh.
• Fixed very rare issue that geometries were not correctly sampled with particles when using Mesh_Independent sampling.
• Fixed mesher files not being copied when saving the scene under a different name using “save as”.
• Data and statistics of deleted objects are now restored for all object types when undoing their deletion (in constrast to only fluids, sources and rigid objects).
• A transform group is now also created for single imported meshes when the create transform group checkbox is checked.
• Fixed issue that wetting sensor data generated with the CLI was sometimes discarded when post-processing the scene with the UI.
• Fixed very rare crash related to changing the frame rate using the property editor.

[2.3.2] - 2018-02-05

Fixed

• Fixed crash that could occur in some cases when a rigid used the “cull rigid particles” option.

[2.3.1] - 2018-01-18

Changed

• Made new rain source properties for varying drop diameters optional, disabled by default.

Optimized

• Improved playback performance for scenes with many objects.

Fixed

• Fixed OpenGL clipping issue leading to a black screen that could occur in very rare cases.
• Fixed threading issue in Preon Renderer that could lead to non-deterministic artifacts.
• Computing a time step that advances to the next simulation frame if there is no active solvers with particles and no active source connected with any solver.
• Fixed issue that right-click actions didn’t work on meshes imported via the new mesh import dialog.
• Added checks for preonpy to have nice error messages when accessing objects from scenes that are not loaded anymore.

Sources:

• Too pessimistic time step prediction with respect to rain source flow rate.
• Time step can not be changed by sources if solver time stepping is not adaptive.

[2.3.0] - 2017-12-14

Added

Sensors:

• Added sensor mesh, which allows you to use the functionality of a sensor plane on a mesh surface.
• The sensor plane now has a property “flow rate mode” that controls how the plane orientation influences the flow rate computation.

Miscellaneous:

• Wetting sensor: Added the possibility to export sensor data on a per-sample basis. Further, the user can choose to export any or all of the values that are measured by the wetting sensor.
• Added new Statistics Resource object. With this object, externally generated statistics can be imported via CSV files and compared to PreonLab scene statistics in the plot dialog.
• Boundary Domains now have statistics printing the fluid volume which is currently scripted and deleted by them and the overall sum of deleted fluid volume.
• Added new mesh import dialog, which allows the user to select which submeshes to import.
• Added progress bar when loading a scene.

Changed

Sources:

• Rain source: Reworked the generation of raindrops. It is now possible to specify minimum and maximum drop diameters to emit varying raindrops consisting of multiple particles.
• Particles generated by a volume source are stored to disk for frame 0. Resuming a simulation from a frame in which the volume source emits does no longer result in duplicated volumes.

Messages:

• The message window is expandable now. By default it is closed, giving more area for the graphics window. Furthermore, there are different tabs for different message types.
• Preon Solver does now only print warnings regarding not being able to load particle data if it expects data to be available.
• Ensight Gold Export now shows a dialog if no solver data exists to export instead of printing a warning.

Timings:

• The overall computation timings have been revised. The total time is now referring to the total time needed for PreonLab to simulate and update from start to end. Thus, every single computation and update process including serialization of data and GUI update times is included instead of just summing up the computation time for collider and physics as was done before.
• By default less timings are printed. Granular timings can still be shown by enabling the new property of the Scene object in OSD Settings named “show granular timings”.
• “prsim” files are no longer written.

Sensors:

• Force sensor: When exporting per-sample data to CSV, you can now choose to export pressure force, adhesion force, friction force and pressure.
• Sensor plane: When exporting per-sample data to CSV, you can now choose to export any or all of the values that are measured by the sensor plane.

OSD:

• Force sensor, Sensor plane, Preon Solver show less statistics in the OSD by default. You can show all statistics by toggling the property “Statistics->OSD Settings->show detailed forces / statistics”.

Import:

• Renamed Adams import to Animation import.
• The Animation import can now additionally also read the PreonLab keyframe format for the animations of the imported meshes. Read the manual for exact format instructions.
• The Animation import now throws better error/warnings if something goes wrong (no animation files found, no meshes found, etc.).
• Improved the handling of mesh and position scaling when importing by providing predefined units.

GL rendering:

• Added “gl auto sleep” setting in the UI settings. If this is enabled (which is the default), PreonLab will disable the rendering of simulation substeps if the user didn’t interact with the GL viewport for at least 10 seconds.
• Accordingly, removed “force repaint” setting in the UI settings.

Miscellaneous:

• Seedpoint is now the new default filling mode for the volume source.
• Parts of the Python library distributed with PreonLab is now zipped to reduce installation time and size.
• Removed close buttons of dock widgets. They still can be closed using “Windows->Name_of_Widget”.
• Tweaked locked/unlocked icons in the keyframe editor.
• Meshes can now be imported via “File->Import->Import Mesh”. This replaces “Add->Solid->Mesh”.
• Changing the path of a mesh resource object does not delete the connections in case the new resource file contains exactly the same number of meshes with the same names in the same order.
• When undoing the deletion of an object, the simulation data is restored.
• No longer creating scene file copies in trash folder.
• Scene saving: When saving a scene under a new name the following new rules apply: a) only folders contain any files in the new scene working directory are created. b) only those resource files are copied which are still used in the scene.
• Scene saving: A warning is given if the user saves a scene as “portable” and the portable folder already contains a mesh file with a file name identical to the name of a mesh file not yet made portable.
• Changed naming algorithm for object creation. The generated unique name now contains the proposed name in case of conflicts.
• When scene loading failed, preonpy.scene is set to an empty scene.
• Force execution of Python code in the PreonLab console by Ctrl+Enter, even if cursor is not at the end of the line.
• Added unit information to tooltips for physical properties like position.
• Dialogs no longer close when pressing enter without focus on the ‘OK’ or ‘Cancel’ button.

Optimized

Performance and memory

• Optimized Preon Renderer performance when used as a post-process.
• Reduced memory consumption during post-processing by up to 50%.
• Reduced memory consumption while simulating by up to 15%.
• Optimized Force Sensor computation performance.
• Optimized Force Sensor visualization performance when using the “show particles” option for the corresponding rigid.

Saving and loading

• Optimized the size of the scene file (.prscene) in general (e.g., by reducing the number of indentation spaces) and by encoding keyframe sequences more efficiently.
• Fixed frame loading efficiency issue when using a scripting boundary domain.
• Rigidstate files only written if there are dynamic objects in the scene.
• Fluids no longer serialize their density buffer. This saves hard drive space.

GUI

• Improved scene inspector UI update performance.
• Reduced number of GL repaints in scenes that simulate very quickly.
• Improved GL OSD rendering performance.

Fixed

Keyframe Editor:

• Fixed issue that the csv import created linear interpolation keyframes for enum or boolean sequences.
• Fixed that “Fit to timeline” did not work if there was no keyframe.
• Fixed that “Fit to curve” did not work properly for very small values.
• Fixed that “Fit to curve” deselects the currently selected key marker in the keyframe scene.
• Fixed that with no keyframes, the line indicating the current property value ended at the simulation end time.
• Fixed an issue that when importing keyframes via CSV all keyframed properties were locked instead of only the sequences with imported keys.
• Fixed issue that undoing a keyframe creation did not restore the property’s previous value in all cases.
• The keyframe dialog is now easily closeable on systems with GNOME 3 if no object is selected.

Sensors

• Fixed Force Sensor measuring very inaccurate adhesion and friction forces when using no-gap.
• Fixed rare crash caused by Force Sensor visualization.
• Fixed issue that pathlines did not serialize their start frame, which could lead to wrong playback.
• Fixed issue that sensor data was not updated when incrementing a frame in playback mode.
• Fixed an issue where incrementing the view frame via the timeline would update collected sensor data (e.g. update wetting times).
• Fixed an issue in the sensor plane loading for sensor planes with property ‘active cells’ set to ‘trimesh’.
• Fixed issue that color legend was still shown for force sensor even after the connected solid was disconnected.

Renderer:

• Fixed minor bug in absorption term of the water material.
• Fixed crash when rendering an inactive fluid.

preonpy:

• Fixed issue that no preonpy.SceneLoadFailed is raised, if a scene could not be loaded 2 times in a row.
• Now preventing connection loops in preonpy.

Miscellaneous:

• Fixed collider not being able to show an OSD.
• Fixed a problem in collider and bullet settings that numbers with more than 5 decimals or larger than 99 could not be inserted.
• Undoing and redoing is not possible anymore during simulation, fixing a possible crash.
• Fixed very rare issue that solids were not sampled correctly with boundary particles.
• Fixed issue that statistics were not written to disk in some cases.
• Scene saving: If the cached data of an object was not copied to the new scene destination (decision by the user), the cache info (e.g. graphical mesh representation, timeline etc.) in the GUI is updated accordingly.
• Fixed floating point precision issue when using the “Compute System” command.
• STL meshes with empty submeshes can be imported now.
• Fixed issue that particle spacing was in rare cases not updated for objects that were copied and pasted.
• Fixed a crash when trying to start PreonLab using ssh -X which is not supported.
• Fixed crash when duplicating objects directly after executing Python scripts, which did not create any object.
• Fixed density-based coloring of fluids.
• Fixed that objects created by pasting using CTRL+V were not directly selected.
• Fixed undo/redo for airflow imports.
• Fixed auto-zoom issue in plot dialog.
• Fixed undo/redo functionality for the “align to gravity” utility.

[2.2.4] - 2017-11-15

Fixed

Renderer:

• Fixed the issue where GL frames would not be written to disk anymore if the PreonLab GUI window was minimized and/or not visible anymore.

Volume source

• Fixed a numerical error in the seedpoint algorithm of the volume source which computed different fill volumes for different particle spacings.

Miscellaneous:

• Fixed one issue that caused PreonLab to freeze occasionally on Windows 7 when the PreonLab window is (partially) occluded by another program.
• Fixed issue that in dialog boxes sometimes no numbers larger than 99 could be inserted.

[2.2.3] - 2017-10-25

Added

Area source:

• property “static source area”: If this property is enabled, the area is only updated when launching the simulation, assuming that the area is static and does not change over time. This can significantly improve performance in some scenes.

Fixed

Connection Editor:

• Connections, that are not displayed, can’t be selected and also will not be deleted when pressing Del.

Area source:

• Optimized area source emission for scenes with no-gap, and scenes where fluid is emitted into high-pressure regions. This prevents fluid leaking the area source in opposite emission direction.

Sensor plane:

• Sensor plane accounts for its velocity when measuring flow rates now. In previous versions, the flow rate was always in global space. This is the new default. Can be disabled by switching new property “relative flow rate” on.

Miscellaneous:

• Warn on problematic characters in filenames for importing 3d models.
• Fixed that sometimes dragger for objects were not appearing.
• Fixed partial hang of PreonLab, when importing of stl files via drag and drop fails.

[2.2.2] - 2017-10-16

Fixed

• Fixed plot dialog not being able to show plots for scenes with very small time steps.
• Fixed possible performance issue when using the static rigid culling feature.
• Fixed issue that inactive sources could negatively impact performance in some cases.
• Fixed potential Adams import crash.
• Fixed crash when executing commands, that print a progressbar when called in the PreonLab console.

[2.2.1] - 2017-09-01

Added

GUI:

• Added ability to export forces (and pressure) for each sample of a force sensor or a sensor plane via action “Export sample data to CSV”.
• Added mode “WettingTime” to the wetting sensor. It keeps track on how long the fluid(s) were in touch with the sensor. Coloring can be used to differentiate wetting times within user-specified ranges.
• Added ability to colorize the mesh of a solid object using the particle coloring.

Video Export:

• Added ability to export images generated by sensors as video using the “Export Video” dialog.

Miscellaneous:

• Added experimental option to scene settings that affects the scheduling of threads to logical CPUs. This can improve performance on multi-socket systems when not using the maximum number of threads.
• It is now possible to copy & paste objects with CTRL+C and CTRL+V.
• Added possibility to compress wetting sensor data (enabled by default).

Preon Renderer:

• Added spray model to Water Material that detects turbulent regions in which water is mixed with air and renders them as spray.

preonpy:

• Added Python bindings for CSV export of ForceSensor and SensorPlane.
• Added Python bindings for Preon renderer.
• Added path and working_dir properties for Scene objects.
• Added read-only property “global position” for all spatial objects which returns the global position considering all transform parents.
• Added raycasting utility.

Bullet:

• You are now able to specify an external collision mesh that is used for rigid body simulation instead of the original mesh. This also allows to create a concave collision mesh based on multiple convex submeshes.

Sources:

• New source type: Flat jet source.

Preon Solver:

• Added statistic showing the number of particles deleted by the solver due to CFL violation or stuck prevention.

Changed

• Established new rules how the conditions of multiple simulation boundary domains are combined. Checkout the manual for a documentation of these rules.
• The wetting sensor now only supports one connected mesh.
• The record statistics, track statistics and inheritance mode properties are no longer keyframable. Also fixed some other minor inconsistencies regarding keyframable properties.
• The path property for file rigids is not displayed anymore if the rigid is connected to a mesh resource.
• The volume source now has an option to automatically set the border size based on the fluid spacing, also considering the no-gap option. This option is on by default for new scenes.
• Added progress bars for boundary sampling and volume source filling for improved responsiveness.
• Preon CLI and preonpy do not link anymore to any OpenGL or X Server libraries.
• In preonpy, color properties do not accept color names (“red”) or short html notation anymore (“#123” must be written as “#112233” now).
• Removed the visualization of the film wetting from the wetting sensor and added coloring option “WettingFilmBased” to solid objects instead.
• The particle limit for sources and solids is now given in mega particles, so a limit of “100” means 100 million particles.

Fixed

Keyframe Editor:

• Fixed undefined behavior in “undo/redo” commands for time/value changes following the selection of a curve segment (i.e. not selecting the key itself).
• Fixed an issue where the curve of a keyframe sequence was not properly updated after a time/value change.
• Fixed issue that allowed to create behavior keys with an invalid value.
• Fixed issue that allowed to use linear interpolation for boolean keys.

Undo/Redo:

• Fixed “Adjust scale to spacing” not creating an undo action.
• Fixed undo/redo issue restoring properties when undoing the creation of an object.
• Fixed undo/redo issue when restoring the creation of a camera resulting in a not updated camera list.
• Fixed undo/redo issue when restoring the creation of a material.

Preon Renderer:

• Fixed issue that allowed to use the water material as hemisphere material, leading to a crash when rendering.
• Fixed rendering issue that could occur when using a no-gap solver and the water material.
• Fixed issue that could lead to distorted output images.

Bullet:

• Fixed that objects with collision shape gImpactMesh did not collide with other objects using gImpactMesh.

preonpy:

• Fixed Scene.simulate_step. It is now implemented as a context manager, so the calling scheme has changed. Consider the API documentation for an example.

Miscellaneous:

• Fixed a startup crash when no OpenGL context could be found.
• Fixed issue when simulating with a scripting boundary domain and an active Preon Renderer.
• Improved error handling for airflow import.
• Removed Group “Transformation” and Property “Color” from wetting sensor.
• Changed coloring range variables from type float to double. Thus, user input is not changed in the property editor.
• Fixed efficiency issue that could occur with certain geometries in Preon Renderer and the Volume Source.
• Fixed issue that clipping planes did not update when they had a scale of zero.
• Fixed issue in plot dialog that smoothing width was sometimes set to 0.
• Fixed misleading color interpolation in color legends.
• Fixed file browsers opened with relative file paths not opening where the relative paths point to.
• Fixed issue when changing the current camera in the Rendering Dialog while rendering an image.
• Objects, that are hidden in the scene inspector, are now also hidden in preonpy.
• Fixed issue that a warning message was sometimes printed in the console when opening the video export dialog.
• Fixed particle type based coloring not showing different colors for scripted and sleeping particles.
• Fixed issue where continuous sources would emit particles differently after resetting and re-simulating a scene.
• Fixed issue in force and wetting sensor when loading a scene which was caused by overwriting particle IDs.
• Fixed crash caused by the wetting sensor when simulating without a fluid.
• Fixed issue that force sensor statistics may differ significantly during playback from the statistics measured during simulation.
• Fixed issue that property editor did not update after locking or unlocking a camera via right-click menu.
• Fixed occasional flickering issue for glossy surfaces in the graphics window.
• The video export can now handle input images in which the width or height is not divisable by zero.
• Fixed issue when using GL recording and switching between camera views.

[2.1.4] - 2017-07-20

Changed

• PreonCLI and preonpy can now be used via ssh without passing the -X option.
• Transform groups now have a simple visual representation.
• Draggers are not displayed anymore if the corresponding property (position, orientation or scale) is hidden.

Fixed

• Fixed wetting sensor issue that could lead to non-deterministic results for some geometries.
• Fixed error in computation of frictional and adhesional forces on dynamic solid objects and in force sensor (when density of solid differed the density of fluid).
• Fixed issue that PreonLab showed a file open dialog when creating File rigids using the preonpy console.
• Fixed issue when creating keyframes from preonpy.
• Fixed issue when starting a simulation from a frame other than zero with enabled progressbar in preonpy.

[2.1.3] - 2017-07-10

Added

• Added property in “Scene -> Statistics -> OSD Settings” to decide on whether and which rigid particle counts are shown in the OSD.
• Added properties for each object for disabling tracking and recording of statistics.
• Read only property which prints rpm converted from revolutions per second (if orientation control mode is set to revolutions per second).

Changed

• “Information” property group renamed to “Statistics” with subgroups for “OSD Settings” and “Statistics Recording” related properties.
• In case there is a “disk full” error, PreonLab now prints the corresponding file path in the error message.

Fixed

• Fixed force sensor issue when using a very small fluid spacing and pressure is displayed in Pascal.
• Fixed unwanted change of current serialization path when pressing OK in user preferences dialog.

[2.1.2] - 2017-06-22

Fixed

• EnSight Gold export: Fixed the bug that lines written to the case file could be longer than 79 characters (causing a warning in e.g. Paraview, because it does not adhere the format specification).
• Addressed the issue that for some versions of avconf (ffmpeg) the start_number for the first input image must be at least 1.
• Fixed issue in the experimental viscosity model Laminar_Morris.

Optimized

• Fixed efficiency issue that could occur when using a scripting boundary domain.

[2.1.1] - 2017-06-09

Fixed

• Fixed pathline playback issue with a non-zero start frame.

[2.1.0] - 2017-06-07

Added

preonpy:

• Added interface to create, delete and query connections.
• Added interface to create and query keyframes.
• You can now use preonpy.scene to get the currently active scene.
• Added a progressbar for simulation and post-processing.
• Added cancel possibility via Ctrl+C.
• Added a read-only property to get the available statistic names.

Plot Dialog:

• Added optional smoothing filter that allows you to remove noise from measured data.
• Added option to use a fixed time step for plotting.
• Added option to toggle automatic updating of time and value ranges during simulation.
• Added additional button for exporting all statistics in the plot dialog regardless of whether they are checked or unchecked.
• It is now possible to show the statistics from multiple objects in a single plot dialog. Select multiple objects and then click on the plot dialog icon.

GUI:

• Added the option to customize the control key (Shift by default, used for e.g. camera control) in the User Preferences.
• Force sensor: Added pressure computation (in Pascal) to show min., max. and net pressure. Further, the pressure can be selected for coloring.
• The console is now based on the preonpy API.

PreonSolver:

• Added one dimensional solver option.
• Added new stopping criterion for pressure solver which also takes the expected maximum density error into account. This is the new default.
• Added additional time-step criterion for viscosity forces.
• Added experimental new viscosity force (Laminar_Morris).
• Added minimum velocity statistic. Coloring now also uses this min. velocity instead of 0.

Preon Renderer:

• Preon Renderer now supports pathlines.

CLI:

• The CLI is now based on the preonpy API.
• The CLI can now execute Python scripts or simulate .prscene files.
• Added a progressbar for simulation and post-processing.
• Added cancel possibility via Ctrl+C.

Miscellaneous:

• Added option to only inherit position or orientation from a transform parent.
• Rigid friction in Bullet Settings of an object is also applied as rolling friction on the rigid object internally.

Changed

PreonSolver:

• Adhesion and viscosity forces have been re-calibrated for no-gap option of solver in order to better match with simulations which have no-gap off (default).

Plot dialog:

• Replaced “fit to plots” button with separate “fit to time” and “fit to value” buttons.
• Redesigned toolbar to make space for new functionality.
• Displaying a new sequence in the plot dialog does no longer auto-zoom.
• If the only displayed plot is a straight line, the auto-zooming is improved by centering the plot and choosing an good zoom-level.
• When no plot is selected, the export button is now disabled.
• The marker dot for the current value of a plot now is always displayed as long as the mouse is in the plot view (no longer disappears when mouse is more than half the vertical plot size away from it).

Alembic:

• The export button in the alembic export dialog is now disabled if no object is selected.
• Importing alembic objects now creates an undo event.
• Importing alembic object without “hotload” now creates keyframes for transformation samples.
• The transformation group in the property editor is now hidden if the property “load transformation samples” is on.

Airflow import:

• Respective delimiters are now automatically detected for csv import.
• Column names can now be chosen via a drop down menu which is automatically filled.
• Import can be canceled.
• More robust import. Can even import some not correctly formatted csv files.
• Better feedback if something went wrong during import.
• Asking user before (undesirably) overwriting existing .prairflow file.
• Changed default discard samples setting form StandardDeviation back to None, as it was in 1.4.1.

Ensight Export:

• It is now possible to choose if the particles should be exported as nodes or elements.
• It is now possible to export the density.

preonpy:

• If a scene open fails, an exception is raised instead of returning an empty scene.
• Removed the silent and default_value parameters from get_statistic and get_statistic_avg. Now an exception is raised in error cases.
• Instead of returning numeric limits on error in get_statistic_min and get_statistic_max an exception is now raised.
• If object deletion failed, an exception is raised now.
• Changed some exception names: PropertyConvertTypeException to PropertyWriteError, InvalidObjectException to ObjectInvalid and several names ending withException to ending with Error.
• SceneLoadFailed is raised when scene load fails instead of ValueError.
• ObjectCreateError and ObjectDeleteError are raised instead of returning None and raising RuntimeError.
• get_property_enum_values now raises PropertyError instead of KeyError if the property is no enum.
• If a property name could no be found, PropertyNotFound is raised instead of KeyError in many cases.

Miscellaneous:

• Removed deprecated property connections. Old scenes containing property connections will write an error message during loading.
• Fluid spacing slots are not shown in the connection editor anymore.
• “Adjust scale to spacing” action is now also available for sources, cuboids and cylinders and planes.
• Bullet collision shape settings are now exposed for scripted and stationary rigids.
• Removed collision margin property. For all solids, the collision margin is now always derived from the fluid spacing.
• Not printing warnings if frame data of continuous sources are not available on disk.
• Changed area source particle alignment so that it is consistent with the square source.
• When a new Preon Renderer is inserted, it is now initialized with the current scene background color.
• Added an option for each object to export statistics as CSV automatically during simulation or playback.
• Added option for pathlines to enable playback over time.
• Added option to set a lifetime for pathline segments during playback.
• Continuous sources now only script the particles they have emitted.
• Scripted particles now compute a correct density. This solves problems when a continuous source emits particles very slowly.
• The CLI no longer contains a command prompt.
• Keyframe Editor: ‘Copy keys’ button is enabled/disabled depending on whether at least one of the selected properties holds a keyframe sequence.
• When inserting a “Point” object, the point is not connected automatically to a volume source as seedpoint anymore. Accordingly, when inserting a volume source, it is not connected automatically to an existing “Point” object to use it as seedpoint.
• When in PrePost licensing mode, the Reset button now is disabled in addition to the simulation button.

Fixed

Keyframes:

• Fixed issue that keyable properties of disabled property groups are still shown in the keyframe editor.
• Prevented the Keyframe Editor from adding enum keyframes with invalid values.
• Fixed keyframe editor not being updated when the visibility of properties changed.
• Keyframe-Editor “Remove for all properties” action: Fixed being asked if deletion of locked keyframe is ok even when no such key will be deleted.
• Keyframe-Editor “Remove for all properties” action now creates an undo-event. This means you can undo the deletion.
• Fixed a problem where two properties were selected in an opened KeyframeEditor when switching between objects.
• Fixed camera keyframing not possible using the CTRL+K and CTRL+L shortcuts.

Plot Dialog:

• It is now possible to zoom to smaller ranges in the plot dialog.
• Fixed crash when deleting an object while its plot dialog is open.
• Fixed crash in Plot dialog when entering an invalid range.
• Fixed plot dialog issue concerning very small time or value ranges.
• Fixed unintuitive cutoffs when entering time ranges in the plot dialog.

Miscellaneous:

• Fixed alembic mesh being not immediately displayed when inserting it via “Add->Solid->Alembic Mesh”
• Fixed preonpy performance issue on some Linux systems.
• Crash when closing PreonLab and the current frame has been changed by user without accepting the change by pressing ‘Enter’.
• Fixed bug when exporting CSV data from preonpy (and probably the CLI) but no data is available.
• Fixed icons in the User Preferences showing the color of a color property.
• Fixed volume source issues when using seedpoint filling in combination with a very small fluid spacing.
• Fixed issue that changes to collision margin were sometimes ignored.
• Fixed issue that “freeze movement” switches for solids had no effect.
• Disabled loading of cached scale transformations from disk during playback for all solid types except alembic.
• Fixed issue that sometimes the bullet collision shape was not created correctly for solids when using a mesh resource.
• Fixed area source such that fluid particles are generated in a deterministic order.
• Fixed bug that scene and view frame rate were reset on scene loading if framerate keyframes were present in the past.
• Fixed precision issue of mesh independent boundary sampling algorithm for very small spacings.
• Fixed bug that allows to set invalid object names from preonpy.
• Fixed issue when loading cached pathlines from disk.
• Fixed unnecessary serializing of rigid state extension.
• Fixed generation of invalid pathline segments for deleted particles.
• Fixed issues with HDPI displays.
• Fixed PreonLab not asking for saving an unsaved scene when loading a new scene via drag & drop.
• Fixed source spacing not being set on a source when two solvers are first inserted and then one is connected to the source.
• Fixed spacing being reset to 0.05 when a second solver is inserted.
• PreonLab now asks if the user wants to stop a running simulation before closing, opening a scene etc. This also prevents a crash when loading a scene with drag & drop while a simulation is running.
• Fixed that inactive objects did not have their data cleaned when reset is pressed. Now, only objects which have their behavior set to cache keep their data on reset.
• Fixed loading of first frame although its already loaded when resetting the scene. This now allows to change properties of dynamic objects in frame 0 without them being overwritten when pressing reset.
• Fixed small numerical deviations in force sensor due to parallelization.
• Fixed issue that an error message was printed when inserting an Area Source without inserting a solver first.
• Fixed platform dependent CSV import issue.
• Fixed loading of ForceField connections between AirFlow and solver objects in old scene file.
• Fixed issue that deleting an object using the right click menu in the scene inspector did not generate an undo/redo event.
• Fixed force sensor legends being shown in the OSD for invisible sensors.
• Decreased the frame limits to 999999 to fix frame writing bug.
• Fixed issue that sometimes the renderer dialog did not clear the status message correctly after rendering finished.
• Added missing spaces in “freeze movement” / “freeze rotation” property names for Solids.
• Added message when attempting to open a non-existing image folder using the renderer dialog.
• Fixed bug that occurred, when adding view frame rate keyframing and the first keyframe was not at time 0.
• The no boundary gap option is now synchronized across solvers, fixing problems for multiphase simulations.
• Fixed a bug where property groups could not be enabled/disabled anymore after they have been multi-selected in the Scene Inspector.
• Fixed a bug that enabling/disabling property groups was not reflected in the view in multi-selection mode.

Optimized

• Optimized rain source performance on systems with many cores.
• Fixed collider performance issue that sometimes occurred in simulations with sparse fluid, typically raining simulations.
• Improved collider performance for scenes with non-moving boundaries sampled with millions of particles.
• Added option for solids to avoid generating boundary particles outside boundary domains if the transformation between rigid and boundary domain is fixed over time.

[2.0.4] - 2017-05-24

Fixed

• Fixed issue when closing an untitled scene with a user-defined cache directory.

[2.0.3] - 2017-04-06

Changed

• Increased the frame limits from 10 thousand to 1 billion.
• Removed deprecated divergence correction properties and functionality.
• Relaxed the stuck prevention criteria default values to be less aggressive.

Fixed

• Fixed mesh with same name as scene file not being found when drag’n’dropped into the scene.
• Fixed potential OpenGL shader issue on some systems.
• Fixed issue that rigids created via alembic or adams import were not deleted correctly.
• Fixed rare crash when closing PreonLab and the current frame has been changed by user without accepting the change by pressing ‘Enter’.
• Fixed bug in CFL deletion criterion for no-gap.
• Fixed issue that scene statistics were erased during playback in special cases.
• Fixed hiding of properties in preonpy when the visibility changes dynamically depending on other property values.
• Fixed issue when switching between rotation modes of spatial objects.
• Prevented creation of transform keyframes using hotkeys when using an incompatible position or orientation control mode.
• Fixed performance issue when using a small integration time step for acceleration keyframing.
• Fixed issue that scene statistics were erased during playback.

Optimized

• Fixed potential performance issue during keyframe creation.

[2.0.2] - 2017-03-20

Fixed

• Fixed crash when deleting the last keyframe of a derived sequence when control mode set to velocity or acceleration.
• Surface offset clamping warning for Box and Cylinder is only shown when the surface offset was actually clamped.

[2.0.1] - 2017-03-17

Fixed

• Fixed issue that source inflow unit “volumeFlowRate” was sometimes overwritten with “velocity” when selecting the source in the Scene Inspector.
• Fixed issue that area sources failed to update their areas in certain rare circumstances.

[2.0.0] - 2017-03-14

Added

Preon solver:

• Added option which eliminates volumetric thickening of boundary. (see no gap option)
• Added PairwiseForce Cohesion model (set as default model). This is an improved version of the PreonCohesion force which is designed to be resolution invariant. Its default parameter of 1 is calibrated for water by TU Dresden. Old scenes using PreonCohesion model are automatically converted to PairwiseForce model.

Creating Scenes:

• You can now set or keyframe the velocity or acceleration of an object. To do so, change the new object property “position control mode” to the appropriate option.
• You can now set rotations per second around an arbitrary axis for an object. To do so, change the new object property “orientation control mode” to the appropriate option.
• Added a message box asking the user whether he intends to change the simulation or view frame rate globally when trying to change the respective value on a frame other than zero. For a variable frame rate, he is informed to employ keyframing.
• Keyframes copied from one selected sequence can now be pasted to one other selected sequence as long as the data type is compatible (e.g. when both sequences have keyframes represented by floating-point numbers).

Preon renderer:

• Added support for rendering water caustics using photon mapping.
• Added Preon Renderer dialog which allows to render single images or image sequences, and displays rendered images. The dialog also removes the need to connect cameras to the renderer object.

Export:

• Added export to the EnSight Gold format.

Python scripting:

• Added Python extension preonpy. This Python library can be used like any other Python Library by importing it with “import preonpy”. This simplifies automatic execution of simulations.

GUI:

• Added a border around context menus to highlight them better from the background.
• Added a ‘Delete’ option to the context menu (right-click on objects in Scene Tree).
• Tooltip for scene inspector items with full object name.
• Separation of time units for better readability in OSD and timeline.
• Added option to turn off camera control using the mouse for specific cameras. You can enable or disable camera control for a camera by changing its “locked” property.
• When multi-selecting objects, the Property Editor now shows the properties sorted in groups similar to single-select.
• Added a User Preferences dialog under the Settings menu that allows to define preferences when creating a new scene.
• Added a ‘maximum number of threads’ option to the User Preferences and a ‘individual #threads’ option to the scene settings which allow to control the number of threads used by PreonLab globally and per scene.
• Added a pop-up window to the ‘Reset’ button of Bullet Options and User Preferences that asks for a definitive confirmation.

Changed

Preon solver:

• Improved time step prediction by splitting up simulation update into explicit force computation, time step adaption, implicit force computation and integration.
• Epsilon usage in CFL-based deletion criterion is now independent of resolution.
• Exposed more options to the user on particle deletion for numerically challenging situations and scenes.
• Improved accuracy for CFL-based deletion criterion.
• Improved performance due to better pre-condition of the pressure solver system.
• Density correction for regions with sampling deficiency.
• Removed “Edit Caching” fluid dialog. You can now enable or disable fluid data caching using the property editor. The properties are located in the new “Serialization” group of the fluid.
• All Preon files storing particle data (.prstate, .prsampling) now use an updated internal file version. This means that old versions of PreonLab will not be able to load particle files generated with PreonLab 1.7 or higher.
• Property group “Compression” renamed to “Serialization”.

Solid objects:

• Removed fluid friction property. Added roughness property which relates the viscosity of the fluid film at the geometry to the property of the solid surface and the viscosity of the fluid in contact with.
• Added warning when Bullet time step is too large which could lead to wrong rigid body simulations.
• Added artificial particle limit for solid objects to prevent generation of too much boundary particles by accident. This limit can be modified by the user.

Sensors:

• Sensor planes now always measure and record all supported fluid properties (velocity, pressure, etc.). The selected property now only determines which data is visualized by the sensor plane. This means that statistics for all fluid properties are always available no matter which property is visualized.
• Improved accuracy of volume sensor with new property “sub particle precision” which accounts for partial particle volume contributions. Is set by default.
• Wetting sensor computes wetting only for connected fluids.

Scene related:

• Recent scene history is correctly restored (also) when not correctly exiting PreonLab.
• When loading old scenes, the user is warned if simulation data need to be converted. If he declines, the old scene and the related data are not modified.

Misc:

• Removed “rotation y axis” property. This is obsolete because you can now easily specify and keyframe the rotation around a specific axis using the new orientation control mode option.
• Scene inspector: Groups now have a fixed order.
• Improved user experience in video export dialog. The slider that controls the playback speed has been removed. Instead, the user provides the input framerate (the number of images per second for the “input stream”), and the playback speed will be computed and shown one line below. If the input framerate matches the “view frame rate”, playback speed is “1x”.
• Removed “underwater reflections” property from the water material (they are now enabled by default).
• Clipping objects are not rotated anymore by default according to up axis.
• Now displaying the number of particles to be generated for a volume source as a property instead of as a statistic.
• In the past, the global transformation of an object was always conserved when connecting or disconnecting a parent transform. This is now disabled when using the orientation control mode “revolution” or “revolutions_PerSecond”, because conserving the local rotation axis is usually more important in these cases.

Fixed

• Stability issues of circle source for very fine resolutions.
• Removed non-resolution invariant scaling of circle source backplane which caused non-plausible behavior for high resolutions.
• Scene inspector: Fixed collapsed groups being expanded automatically after adding/deleting an object.
• Issue in post-processing dialogs when using separate view and simulation framerates.
• Renaming an object to a name already assigned to another object.
• Rename mandatory standard objects.
• Camera/selection mode being stuck, when clicking both mouse buttons at the same time.
• Issue where the visibility of nodes in the connection editor was not correct after removing connections.
• Active camera and quad view state were not correctly loading from scene file.
• Sensor plane issue that occurred sometimes when changing the framerate and reloading the scene.
• Occasional startup crash on specific linux distribution.
• Issue where a safe file dialog would not add the selected file extension to the filename.
• Alembic export issue for objects with transform parents.
• Alembic export issue for scenes with another frame rate than 50.
• Issue with different (keyframed) view frame rates and video export. Videos can now only be generated piecewise, one video per keyframe, thus, preventing the misinterpretation of the number of rendered images per second.
• Fixed Area Source border issue.
• Problem of hugely scaled point objects when they are not in screen space, but camera zooms in on nearby region.
• OSD is now displayed again (if requested) for non-spatial objects such as Preon Renderer.
• Fixed some inconsistent namings in PreonLab and in the manual.
• Fixed inconsistent display names and tooltips of some properties.
• Copy resources dialog now lists OpenGL frames if present.
• Fixed water rendering artifacts at the transition between fluid and rigid.
• Fixed Bullet reset bug.
• Fixed the number of particles to be generated shown with the scale dragger when scaling a volume source.
• Fixed issue that renaming cameras had no effect on the camera selection menu.
• Fixed issue that sometimes the floor grid was clipped by clipping planes.
• Fixed PreonLab loading the wrong last simulation frame if an exception is caught during simulation.
• Fixed that Preon renderer and Preon mesher used more threads than allowed by the user.
• Fixed possible floating point precision problem in area and volume source.

[1.4.1] - 2016-11-24

Changed

• Keyframe-editor: Paste button is correctly disabled when clipboard is overwritten by other application.
• Boundary domains: The scripted velocity for velocity condition is now keyable.

Fixed

• Video-Output: Some framerate ratios (e.g., 400 sim frames to 50 video frames) could not be exported. Now all ratios should be possible.

[1.4.0] - 2016-11-14

Added

• Added ability in the connection dialog to also show nodes that are connected to the selected ones.
• Added a button in the connection dialog to view selected objects by zooming out and/or moving the view.
• The positions of nodes in the connection editor are now saved in and restored from scene files.
• In the connection dialog, nodes can now be grouped to perform following tasks: add multiple connections at once, remove multiple connections at once, gaining better overview in large scenes, move multiple nodes around in the connection scene at once.
• Added close button to connection dialog.
• Added DivergenceBased and VorticityBased coloring of fluid particles.
• In the keyframe editor, keyframes of a property can be locked to prevent further editing. Imported keyframe data is locked automatically, too. Locked keyframes can be unlocked.
• In the keyframe editor, keyframes can be copied to the clipboard and pasted to other objects, even across PreonLab instances.
• In the about dialog, the link to the current log file is now clickable.
• Added a measure tool that simplifies measuring distances significantly.
• Added a velocity offset property to the air flow.
• Added Liu Drag Model for the Drag Force which considers deformation of single particles.
• Drag force now displays global velocity when rotating it via draggers and as read-only property in the Information group.
• Added export dialog which simplifies the creation of a video from the rendered images.
• Area source which allows you to emit fluid from an area bounded by solid objects.
• Extended .prstate file format which now supports lossless and lossy particle compression.
• Preon solver now supports on-the-fly particle compression, saving disk space by a factor of 2 to 3.
• Added option to compress existing particle data when saving the scene via “save as”.
• Added archiving option to only keep data of every x-th frame when saving the scene via “save as”.
• Added view frame rate which can differ from the simulation frame rate. This allows for example to post-process/render frames with a different frame rate than saving particle data to disk.
• Added property to Preon renderer which allows to decide if the fluid should cast a shadow.

Changed

• New icons for placement and measure mode, as well as locked/unlocked and copy/paste keyframes in the keyframe editor.
• MemoryLocationBased fluid coloring now also displays a color range in the OSD.
• RigidNeighborhoodBased fluid coloring is fixed and now colors correctly after the size of the neighborhood (not on/off if there are more than 18 neighbors) and shows a color range in the OSD.
• idBased fluid coloring is now named ParticleTypeBased to better reflect its type. Loading old scenes will not automatically convert idBased coloring to ParticleTypedBased coloring. Instead, VelocityBased coloring will be set.
• In the keyframe editor, the time is snapped to the frame time when moving the mouse across the view. Thus, new keyframes are created (and existing keyframes are moved) in frame time steps.
• In the keyframe editor, new keyframes can be manually defined and added via a button.
• Made the ‘inflow arrow’ that shows the inflow direction of a square/circle/rain source an actual arrow (instead of a cylinder).
• Adjusted the scaling of the ‘inflow arrow’ that shows the inflow direction of a square/circle/rain source according to the source’s scale.
• Selected nodes are now highlighted in the connection editor.
• ForceSensor now always logs every force. The toggles only decide which force contributions are displayed. This also fixed a bug that the adhesion force could not be toggled.
• “Memory consumption” action is now an action of the scene instead of the UI Settings (accessible via right-click).
• The arrow displaying the drag force air velocity is now 3D instead of 2D lines.
• Reduced the memory consumption of sensor planes.
• The size of (transformation) points is now fixed in screen space. This means that when zooming in and out the point always appears the same size on the display.
• Moved “save as portable” functionality into the new “save as” dialog.
• Added a progress bar to “save as” dialog.
• Default rigid-sampling method is now Mesh_Independent.
• Default near clip of cameras is now 0.01 and far clip is 1000.
• Whenever a new scene is created, the number of threads is now set to the maximum number of CPU-threads available.
• Removed behavior property of Transform groups as keyframed transformation are always applied.

Fixed

• Fixed not being able to place objects on fluid particles with the placement tool.
• Fixed a minimally too large force being measured by force sensor.
• Fixed removing and then undo-ing of static objects creating new objects.
• Fixed duplicating an object with a transform parent not keeping its global transformation.
• Fixed camera rotating to unit axis when looking straight up.
• Fixed osd being transparent in GL recording.
• Fixed not being able to manually change the path in mesh resources.
• Fixed a problem that sensor planes wrote a csv file in the wrong directory.
• Fixed cylinder lighting issues due to wrong normals when either top or bottom cap are switched off.
• Fixed the drag force arrow not rotating with the rotation of the drag force.
• Fixed issue with time step clamping to frame time which could lead to CFL-based particle deletion in rare cases.
• Fixed issue that active camera view was not reset when creating a new scene.
• Fixed issue of unresponsive and disappearing progress dialogs.
• Fixed issue that dragger of viewing camera could be visible in rare cases.
• Fixed issue that statistics concerning the start frame were not written during playback.
• Fixed an issue that the circle source did not continuously emit particles when only a single particle fits in its diameter.
• Fixed Alembic Rigids that have “load transformation samples” set to “off” not correctly loading orientation when loading a scene.
• Fixed PreonLab overwriting existing, user-created folders when a scene with same name is saved.
• Fixed issue that playback still was on after pressing reset without pausing simulation.
• Fixed bug that “Clean data” did not clean statistics and failed to update the GL view and the timeline.
• Fixed GL recording issue that occurred on some systems when the OSD was disabled.

Optimized

• Improved Preon renderer load balancing, resulting in better CPU utilization for many setups.
• Improved timeline responsiveness.
• Inactive solids are not sampled anymore with boundary particles.

[1.3.1] - 2016-10-05

Changed

• The columns in csv-exported statistics are now always ordered alphabetically.

Fixed

• Fixed Adams import mapping angles larger than 180° to the range -180° to 180°. This is a specific fix that only works when the rotation axis is one of the unit axes.

[1.3.0] - 2016-08-17

Added

• Added a check box to the keyframe editor to enable/disable updating the time on click in the graph.
• Added mesh resource object which loads a mesh file and provides an outgoing slot for each loaded sub-mesh. This makes it possible to have multiple individual rigid objects for a single mesh file (typically stl).
• Dragging and dropping a mesh file now creates a mesh resource and one connected rigid for each loaded mesh.
• Added a new column to the scene inspector that shows an icon if an object is invisible in the according line.
• Added undo/redo support for MSC Adams import.
• When importing Adams data, a transform group is now automatically created and connected to all imported objects.
• Added Core.postProcess(startFrame, endFrame) method to PreonLabCLI.
• Added position and velocity statistics (and plots) for rigid objects.
• Added new alternative boundary sampling algorithm that generates fewer and more uniformly spaced particles for high-poly meshes than the current algorithm. This fixes leakage and performance problems that could occur in rare cases with the current algorithm. Currently, the main disadvantage of the new method is that pre-processing is much slower than with the current method (it is still well under a minute for most scenes though). The new boundary sampling can be selected by setting the “boundary sampling method” property of the rigid to “Mesh_Independent”.
• Added vdafs resource object which imports transformation data from vda-files and provides them as a transform output slot.
• Preon Renderer now supports Force and Wetting sensor.

Changed

• The up axis is no longer a property of UI Settings object but instead is a property of the scene now.
• Made z-axis the default up axis.
• In the keyframe editor, updating the time on click in the graph is now disabled by default.
• Moved collision shape properties of meshes into Dynamic Settings group which is only visible when type is set to dynamic.
• Cameras with orthographic projection can now be rotated just like perspective cameras.
• When a pathline has a transform parent, it generates pathlines in local space relative to this parent. This makes it possible to see fluid motion relative to a moving object, for instance water sloshing in a moving tank.
• Clipping plane is now replaced by clipping object, which also supports clipping inside or outside a box.
• Cameras now behave more consistent if you attach them to a rotating transform parent. If the property “fixed up axis” is disabled, they also perfectly rotate with their parent allowing to view an object always exactly from the same relative position.
• Removed Camera lookat property. You can still specify a lookat by connecting the Transform of another object to the new Lookat camera input slot.
• Input fields for numbers in the Property editor now allow to insert number in scientific notation (e.g. 1e-05)
• Dialogs now use improved Input fields for numbers similar to the ones in the property editor (e.g. Bullet-Settings)
• Scrolling the mouse wheel when focusing a spin box or combo box in the property editor no longer changes the value.
• Changed the “Camera” menu and scene inspector group name to “Rendering”.

Optimized

• Deleting a lot of keyframes in the keyframe editor at the same time is now faster.
• Improved the performance of the plot dialog when drawing large graphs.
• Improved force sensor rendering performance.

Fixed

• Fixed that multiple undo events are created when deleting multiple keyframes in keyframe editor at the same time.
• PreonLab now throws an error message when trying to load a scene file with a newer version than the current program-version.
• Fixed Preon Renderer clipping issue.
• Fixed being able to close a connection loop which lead to a crash of PreonLab.
• Fixed the connection editor not showing connections to a duplicated object.
• Fixed inconsistent state when continuing an aborted simulation due to missing disk space. Most previous non-corrupted state is loaded from disk.
• Fixed issue when keyframing a camera without fixed up axis.
• Fixed crash when calling PreonMesher.meshSequence(start, end) in PreonLabCLI
• Fixed Preon Renderer issue when hiding scripted particles.

[1.2.3] - 2016-07-05

• Fixed issue that camera matrices were not updated correctly by Preon Renderer.
• Fixed issue that sleeping particles were not rendered in some cases.

[1.2.2] - 2016-06-29

Added

• It is now possible to set the zoom of an orthographic camera in the property editor.

Fixed

• Fixed Preon Renderer clipping plane issue.
• Fixed undo/redo clipping plane issue.
• Fixed force and wetting sensor issue.
• Fixed background image not resetting when creating a new scene.
• Fixed calling “Core.simulateBlocking(start, end)” twice resulting in wrongly cached particle frames in PreonLabCLI.
• Made scene file saving more robust, for instance if there is not enough memory.

[1.2.1] - 2016-06-17

Fixed

• Fixed issue that particles emitted by circle or square source were deleted under rare circumstances.
• Fixed crash when loading scene without solver settings (broken prscene-file).

[1.2.0] - 2016-06-13

Added

• New alternative boundary handling for Preon Solver.
• Added the possibility to specify a position and velocity scaling factors when importing airflows from csv files.
• You can now create materials and assign them to rigids and fluids using the connection editor.
• Added water material allowing realistic water rendering with Preon renderer.
• Preon renderer now renders sensor planes.
• Added Distance Sensor.
• Added Placement Tool.
• PreonLab now notices when the writing of simulation data to disk failed (e.g., when the disk is full) and aborts the simulation showing a warning dialog.
• Added ‘CTRL + H’ hotkey to toggle through the render modes of an object (allows to make the object invisble/visible very fast).

Optimized

• Improved performance of keyframe editor when displaying a large number of keyframes.
• When using simulation domains to script fluid particles, the scripted fluid particles now have less memory and performance impact than normal fluid particles.

Changed

• Removed the position and orientation offset when importing Adams data, this can be done via transform groups. Changed start frame to start time.
• Adams data is now imported as keyframes. This should fix continued problems with reloading the scene and loosing the animation data.
• Clipping planes now operate now per object and per camera. Only connected cameras and objects are clipped.
• If twoSidedLighting is off, backface culling is enabled to avoid lighting artifacts when rendering two-sided geometries.
• Changed the default density of water to 998.2071 (literature value at 20°C) and drag force air density to 1.2041 (also literature value at 20°C).
• PreonLab now shows a warning dialog when the exporting of CSV data from the plot dialog fails (e.g., due to missing rights to export to the provided folder).
• Added switch to connection editor that allows to hide or display property connections.
• Simulation boundary domains now only delete fluid particles by default, because deleting rigid particles can hurt performance in some scenes.

Fixed

• Fixed not being able to scale circle source with the z-axis dragger.
• Fixed typo in the default name of an AirFlowBox.
• Fixed cropping of simulation data.
• Fixed the scaling speed of when using the scale dragger to be dependent on the zoom of the camera.
• Changing the up axis in UI settings now also changes the up-axis of all perspective cameras. This fixes some bugs related to camera movement and rendering with Preon Renderer.
• Fixed simulation step in the bottom left of the OSD not resetting when playbacking or jumping in the timeline.
• The plot dialog can now show larger value ranges. This should fix problems in scenes with large numbers of particles.
• Fixed creation of a keyframe when double-clicking exactly at the same vertical position as an already existing keyframe.
• Fixed disappearing objects (mainly sources).
• Fixed rain source threading issue.

[1.1.2] - 2016-05-18

Fixed

• Fixed wetting sensor related crash.
• Fixed PreonRenderer related crash.
• PreonRenderer now supports cameras with orthogonal projection.
• Fixed camera controller issue in case the camera has a transform parent.

[1.1.1] - 2016-04-28

Changed

• Alembic rigid can now be used as transform parent.

Fixed

• Fixed volume sensor not recording statistics in post-processing mode.
• Fixed crash when deleting PreonRenderer.
• Fixed rare crash in BVH collider.

[1.1.0] - 2016-04-12

Added

• Added Preon Renderer, a raytracer which renders fluid surfaces directly without meshing
• Added the possibility to specify which parts of the OSD are shown in recorded frames.
• Improved plot widget: It is now possible to specify x and y range. Also, it is possible to assign custom colors to plots by clicking on the color in the list of statistics.
• Renamed Sinks to Boundary Domains which can now also remove particles of solids, allowing to create holes in geometries.
• Added velocity boundary condition for Boundary Domain.
• Added possibility to specify volume source alignment via IOAlign slot.
• Added Volume sensor that measures the fluid volume in a orientated cuboid.
• Preon Solver has now the option to restrict the simulation to two dimensions.

Changed

• Surface offset is no longer settable for rigid objects. For boxes, this also means, that the displayed mesh changes and a rigid body simulation would behave differently. For fluid simulation nothing changes.
• Extended and renamed sinks to Boundary Domains and Conditions.
• Preon Solver now allows to specify three colors for coloring its particles.

Fixed

• Keyframes are now also duplicated when duplicating an object.
• Fixed bug which caused transparent areas in recorded frames.
• Fixed seldom occurring bug that sensor plane data cannot be read from disk.
• Fixed remaining parent transform pick highlight after deleting of IOTransform connection.
• Fixed issue that some sensors could not be connected via the IOTransform slot.
• Fixed exclusive range rendering in Preon solver.
• Fixed rare volume source seedpoint filling issue.
• Volume source border size now works correctly for box and cuboid objects.
• Fixed BVH collider bug that could occur when keyframing a rigid from active to inactive.
• Fixed occasional warning regarding the reading of a state-file when the behavior of a continuous source was keyframed.
• Velocity projection and height fields now immediately update their image if a solver is (dis-)connected.
• Fixed continuous sources sometimes emitting inconsistent particles after jumping in timeline and re-simulating.
• Fixed being able to single-step beyond the playback/simulation end-frame.
• Fixed blue simulation indicator bar in timeline always starting from frame 0, even when simulating from a later frame.
• Fixed fluid particles not being removed when jumping to a frame with no particle data file.

[1.0.2] - 2016-04-07

Added

• Added post-processing license.

[1.0.1] - 2016-03-02

Fixed

• Force sensor is now only measuring data for connected fluid.
• Recorded images do not have an alpha value anymore. There was a mismatch between rendered and recorded image due to alpha values.
• Made gradient computation numerically more robust. Prevents unplausible large accelerations / or unintended particle deletion in rare cases.

[1.0.0] - 2016-02-22

Added

• Added a “Recent Scenes” menu entry under “File” which allows quick loading of recently opened scenes.
• Added check on start-up if the current computer fulfills all requirements for PreonLab.
• Added possibility to duplicate multiple selected objects.
• Added possibility to move multiple selected objects using a dragger.
• Viscosity model for PREON solver can be set by user.
• Cohesion model for PREON solver can be set by user.
• Added PREON viscosity model which is invariant with respect to resolution.
• Added PREON cohesion model.
• Added velocity particle killer that kills particles above a specified velocity magnitude.

Changed

• Improved transparency. It is now possible to specify an opacity between 0 and 1 for rigid objects, fluid solvers and fluid meshers. Also, multiple transparent surface layers are now supported. However for efficiency reasons, the result is still only an approximation of real transparency.
• Scene file now stores which camera is active and if quadview is used.

Fixed

• Fixed clean data action not working. Also added clean data action to PREON Mesher.
• Fixed alembic rigid ignoring its parent transform if present.
• Fixed particles not being rendered when using orthographic cameras with inverted direction.
• Fixed background image not working.
• Fixed two-sided lighting.
• Fixed killer fields sometimes killing particles during playback.
• Fixed Recording issues on RHEL6.

Optimized

• Fixed performance issue of BVH collider that occurred after simulating a few hours.
• Slightly improved performance of BVH collider.
• Fixed memory leak in BVH collider when deleting fluids or rigids.
• Improved performance of PREON Mesher when generating very big meshes.