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PRT Loader

Particle Loaders

Krakatoa manages the loading of particle files and sequences via so-called "Krakatoa Particle Loader" scene objects.

Particle Loaders (a.k.a. PRT Loaders) are geometry class stand-in objects which are non-renderable in renderers other than Krakatoa.

Supported input file formats currently include:

Creating Particle Loaders

Particle Loaders can be created

  • by going to the Create Panel, Geometry, Krakatoa category, PRT Loader button
  • directly from the Krakatoa GUI by pressing the [Create New Loader...] button. This will save up to 5 clicks as it creates the object in the scene, selects it in the Modify Panel and pops up the Load File Sequence dialog so the user can pick the files to load immediately.

Features

Particle File Sequence Controls

This section of the PRT Loader contains the list of files to be added and related controls for adding and removing file sequences.

  • Add Files... - this button opens a file picker dialog. The path the dialog will display depends on the Preferences settings for PRT File Loading or the selection in the PRT Loader's file list:
    • If the file list contains no entries (freshly created PRT Loader), the dialog will show, depending on the Preferences,
      • The path currently specified in the Save Particles area of the Main Controls rollout.
      • The default path specified in the Preferences rollout.
      • The current path
    • If the file list contains sequences and one sequence has been selected, the file dialog will show the path of the selected sequence. This is useful when adding more partitions to an existing partition. Note that since the list is a multi-selection box, you can deselect all sequences by holding Ctrl and clicking the selected sequence. If nothing is selected, the behavior specified by the Preferences will be used.
    • New in v1.1.0 If a valid Default Path has been specified in the Preferences rollout, holding down the CTRL key while clicking "Add Files..." will open the dialog at the Default Path regardless of the above rules.
  • The user can select either a single file or a file which is part of a sequence or of a Partition Sequence.
    • If the file is not a part of the sequence, it could be used together with the "Load Single Frame Only" discussed later on this page to display a static particle cloud on all frames.
    • If the file is a part of a numbered sequence, the sequence will display the frame corresponding to the current scene time. If there is no file for that frame, Krakatoa will fail to load the file and will not render/display anything. See Particle Counts rollout for indication of missing frames.
    • If the file is a part of a numbered sequence but the "Load Single Frame Only" is checked in the Timing controls, the frame picked during the adding process will be displayed on all frames. Thus, it makes sense to select a representative frame from the sequence when picking a sequence of frames.
    • The PRT Loader will NOT allow the SAME frame of a sequence to be added twice to the list, but different frames from the same sequence (for example particles_0000.prt, particles_0010.prt, particles_0042.prt) CAN be added to the same PRT Loader so it is possible to show them all at the same time when "Load Single Frame Only" is on. When it is off, the same sequence will be loaded 3 times, thus increasing the density of the cloud and the loading time.
    • If the file is a part of a Partition, a Prompt dialog will appear asking about loading all partitions or the current partition only. Answering with Yes will load any partitions in the range specified in the selected file name, but ONLY if the corresponding frame can be found in the same folder. For example, if the selected file is called particles_part1of3_0000.prt and you answered with Yes, the PRT Loader will attempt to load sequences named particles_part2of3_0000.prt and particles_part3of3_0000.prt. If the file particles_part2of3_0000.prt is not in the folder, even if other files from that sequence like particles_part2of3_0123.prt are in the folder, the partition will not be loaded.
  • The selected files will be shown in a listbox where they can be selected individually or as a group.
  • Double-clicking the file name on the list will open a Windows Explorer at its path (if still existing).
  • Pressing the Remove... button will remove all sequences highlighted in the list box. A prompt will ask for confirmation of this operation as it is not undoable.

File Sequence Manager (Edit...)

See details in File Sequence Manager topic...

Viewport and Render Controls 

 Available in Krakatoa v1.1.0 and higher
  • Every sequence on the list is prefixed by two letters representing the Viewport and Render status of the files. "v" denotes the Viewport display and "r" means the sequence will render.
  • When the sequence is not going to be displayed or rendered, the letter will be replaced by "--".
  • You can select any number of sequences on the list and toggle their Viewport and Rendering state using the checkboxes "Viewport" and "Render" underneath the file list. When the selection contains sequences that have either states, the checkbox will be in an indeterminate display mode (grayed out background and checked).
  • Note that the File Sequence Manager provides a wide range of operations to mass-control the states of the Viewport and Render flags.

Timing

The Timing controls can be used to alter the playback of the PRT sequences. By default, particle sequences are loaded according to the scene time. For example, if a file is called parts_0000.prt, on frame 1 a PRT Loader would attempt to load the file called parts_0001.prt, on frame 42 it would attempt to load part_0042.prt and so on. If the file is missing, nothing will be displayed and if rendered, the rendering will fail.

  • Load Single Frame Only - if the file parts_0000.prt specified in the file sequence list should be used on all frames, checking this option will take the file name as it was specified and use it without attempting to replace the frame number suffix. This can be used to place static particle clouds into the scene.
  • Use Playback Graph - this option switches the loader to a special mode in which the current scene time is ignored and does not flow anymore. It is combined with a Playback Graph spinner defining the frame to be displayed at any given time.
    • When the Playback Graph spinner is set to a static value, for example 5.0, the frame 0005 will be loaded on every frame.
    • The Playback Graph spinner is animatable, so it allows the value to be animated freely over time.
    • The VALUE of the controller at any given frame will define the frame to be loaded on that frame. For example, a straight line from frame 0 with value 0 to frame 100 with a value of 100 would match the normal playback of the PRT loader with Playback Graph disabled.
    • This mode can be used to loop back and forth, change speed, play backwards, play back random frames and so on by specifying matching values in keyframed or procedural controllers. For example, setting a key on frame 0 with a value of 10.0, a key on frame 40 with a value of 30.0 and a key on frame 100 with a value of 0.0 will play back frames 10 to 30 in the interval from 0 to 40 and then backwards from frame 30 to 0 in the interval from 40 to 100.
    • Using bezier controllers, the interpolation of the curve can be used to speed up and slow down gradually etc.
    • The PRT Loader will interpolate particle positions requested at sub-frame steps based on the closest saved particle file sample and the saved velocity (if available).
    • NOTES:
      • This feature is very similar to the Playback Graph found in the Point Cache modifier in 3ds Max 9 and higher.
      • The Frame Offset is still taken into account, so if you keyframed a custom animation in the Playback Graph but wanted to shift it by 10 frames, you don't have to move the keys up in TrackView (although you could), but can just change Frame Offset from 0 to 10.
  • Frame Offset - this spinner can be used to offset the frame counter so instead of loading frames 1 to 10 on frames 1 to 10, entering 5 would load frames 6 to 15 on frames 1 to 10. This spinner is disabled when Load Single Frame Only is checked.
  • Limit To Custom Range - this checkbox limits the frame numbers to avoid attempting to load non-existent frames. The Range spinners can be used to specify the first and last existing frames of a consecutive sequence of frames without gaps. Any attempts to load a lower or higher frame number (because of the current time, Frame Offset, extreme Playback Graph values etc.) will be prevented by clamping the frame number to the lower or higher limit. Thus, if the sequence is set to 0 to 100, the PRT Loader will never attempt to load frames -1 or lower and 101 or higher even if these have been requested due to the timing settings. Instead, frame 0 will stand in for any negative frames and frame 100 will be shown if the requested frame has a number higher than 100. 
 Available in Krakatoa v1.1.0 and higher
  • Set Using Existing Frames - this button can be used to determine the optimal Limit Range based on the actual availability of frames. It will query the frame numbers of all sequences and attempt to find the intersection of all ranges that would display and render without any missing frames. In some cases, such range cannot be determined - if this is the case, a warning message will pop up.

Options

The Options group of controls provides additional control other the behavior of the PRT Loader.

  • Use Node Transforms - controls the transformation of particles by the PRT Loader's node transforms.
    • When unchecked, the particles will appear at the absolute position they were saved at, regardless of the location of the PRT Loader.
    • When checked (default), the transformations of the PRT Loader node will be applied to the particles from the file, thus allowing you to position, rotate and scale the particle system in world space.
      • If the Position and Rotation are zero and Scale is 100%, the particles will appear where they were saved from, equivalent to unchecking this option.
      • Transformations will affect the particle velocities, resulting in correct motion blur of both static and moving particles.

Rendering Rollout

The Rendering Rollout allows the user to customize the count and display of particles in the final rendering.

  • The Load Mode drop-down list provides the following options:
    • Load Every Nth Particle - balances loading through the files skipping particles to reach the final count. If the particles are ordered (for example saved from geometry primitives, or emitted over time), this mode will display a lower particle count that would still represent the overall shape of the particle cloud correctly. On the negative side, this mode requires each PRT file on the current frame to be opened and read from start to end, making this mode the slower one.
    • Load First N Particles (default) - loads from the beginning of the PRT file until the desired count is reached. If the particles are ordered (for example saved from geometry primitives, or emitted over time), this mode will show only a small region that is unrepresentative of the overall shape of the particle cloud, but since loading just a portion of the file is much faster than reading the whole file, it was made the default setting. If the particles in the cloud are completely random (unordered), the result of this mode will look like the result of Load Every Nth Particle but without the speed hit. 
 NOTE that when loading a CSV file, particles will always be loaded in Load Every Nth Particle mode.
 This is because the CSV file does not contain any header information about the total number of particles
 stored inside, and figuring this out on the fly would defeat the purpose of the Load First N Particles mode
 which is used mostly for improving speed. 
 If you need to load particles in the order they were saved to achieve a special effect like building up 
 an object by animating the Render Percentage, you should convert your CSV files to PRT files by loading 
 in a PRT Loader and saving from Krakatoa to PRT, then use the PRTs in the PRT Loader to achieve the effect.
  • The Percent spinner defines the percentage of particles (either first N or every Nth) to be rendered. The Percent spinner is ANIMATABLE, allowing for animated reveals and dissolves of particles over time by changing the percentage of particles loaded from the PRT file.
  • The checkbox in front of the Percent spinner controls whether the particles will be rendered at all. When this checkbox is unchecked, the PRT Loader will not be considered by the renderer at all - as if it was hidden or non-existent. NOTE: You can uncheck this checkbox if you are saving particles to PRT files and the output PRT path is loaded in your existing PRT Loader. Otherwise an error would be reported about attempting to recursively save into a file that is already used for input.
  • The Limit (x1000) spinner provides an optional top limit. Its value is taken as a multiple of 1000. By default it is disabled (checkbox in front is unchecked) and is set to 1000, resulting in a limit of 1 million particles. This can be used if your PRT files contain a lot more particles than you can render and you want to cap the number to a value you know your system can handle safely.
  • The Particle Color Source drop-down list controls the source of the particle color and provides the following options:
    • Saved Particle Colors (default) - uses the colors saved in the PRT file. If no colors were saved, the default color of white will be used for all particles.
    • Loader's Wireframe Color - uses the wireframe color of the Particle Loader.
    • Loader's Material Self-Illum. - uses the self-illumination color of the material assigned to the Loader. If no material is assigned, the particles will render with the loader's wireframe color.
  • The Density->Mapping # checkbox and spinner allow the copying of the Density channel into an arbitrary Mapping Channel where Channel 0 is the Vertex Colors channel, Channel 1 is the TextureCoords channel and channels 2 to 99 are the additional mapping channels added in 3ds Max Release 3. When the checkbox is checked, the content of the Density channel will be duplicated into the specified channel AND the Density channel itself will be reset to 1.0 automatically.
  • The Assume Density of 1.0 ckeckbox allows you to override the content of the Density channel with a default value of 1.0. This can be used when the Density channel is present but has to be ignored or when its content is incorrect (for example, RealFlow BIN files contain a default Density channel containing zeros which would make the particles unrenderable!)
  • [v1.1.0] The Names of the Percent and Limit spinners are now displayed by buttons. Pressing these buttons will show a context menu of typical values and allow the adding and removing of values to/from the list. This functions similar to the [>>] buttons in the Krakatoa GUI.

Viewport Rollout

  • The Load Mode drop-down list provides the same controls as the Render Controls list plus one additional
    • Load Using Render Mode - uses whatever mode is set in the corresponding Render Controls drop-down list.
  • The % of Render spinner defines a Percentage of the Percent in Render Controls. Thus, if the Render Percent is set to 50 % and Viewport % of Render is set to 10%, only 10% of 50% will be drawn in the viewport, in other word only 5%. this also allows you to animate the Render Percent and have the Viewport show the same animation, but with a reduced count.
  • The checkbox in front of the % of Render spinner controls the drawing of particles in the viewport. When it is unchecked, no particles will be drawn. When it is checked (default), particles will be drawn. This option is completely independent from the one in the Render Controls area - particles can be set to render and display, not render but display, render but not display and not render and not display.
  • The Limit (x1000) spinner is similar to the one in the Render Controls, but caps the number of particles to be drawn in the viewport if the checkbox in front of the spinner is checked. The value is set to 100000 particles and is disabled by default.
  • The Color Source drop-down list is identical to the one in the Render Controls but provides an additional option
    • Colors Using Render Mode - uses whatever mode is set in the corresponding Render Controls drop-down list.
  • The Display Mode drop-down list is unique to the Viewport Controls - it defines the shape of the individual particles drawn in the viewport. The options are:
    • Display As Small Dots - draws small dots. The size is dependent on the graphics driver - in Software Z-Buffer, the dots will have a size of exactly one pixel, in DirectX they are usually 2x2 pixels. This is the same mode used by PFlow Dots display. NOTE: In this mode, z-buffering will not function correctly and the particles will not be sorted correctly with regard to each-other and geometry objects in the scene.
    • Display As Large Dots - draws large dots. The size depends on the graphics driver, but is generally much larger than the previous mode. In contrast to Small Dots, Large Dots respect Z-buffering correctly and will sort / intersect with scene geometry as expected. This mode is recommended when working with the Culling option as it would show the correct intersection between geometry and particles in the viewport.
    • Display Velocities - draws lines with size based on the velocity stored in the PRT file. The display is also dependent on the graphics driver - in Software Z-Buffer, velocity of 0 is displayed as a single dot. In DirectX, near zero and 0 velocities make the lines completely disappear. Thus, this mode should only be used when the particle file contains moving particles. This mode is similar to the Lines display of Particle Flow, but is implemented differently:
      • Krakatoa displays lines 30 times faster than the Line display of Particle Flow and about as fast as the Dot display in both Particle Flow and the PRT Loader itself.
      • Particle Flow tests against zero velocity in Line mode and displays such particles as Dots instead of Lines. Krakatoa does not do this as it would require a test for each particle and would potentially slow the display down, especially with millions of particles. If your particles are static, simply do not switch to Velocity Display.
      • If the Particle Loader has been limited to show only one frame, for example via "Load Single Frame Only" checkbox, Playback Graph with no animation or "Limit to Custom Range" with the same start and end frames, NO VELOCITIES will be displayed since the particle cloud is considered static.
    • [v1.1.0] Display Normals - draws the normal vectors as lines. Similar to the Velocity Display, but the lines will point in the direction of the particle normal (if any). The Scale Normal can be used to make the lines appear longer in the viewport. The default scale is 10.0.
  • The Display Bounding Box checkbox is on by default and causes a bounding box to be drawn around the displayed particles. Note that when using Particle Culling, the original bounding box pre-culling will be displayed to show where the particles would have been if they were not culled.
  • The Icon checkbox allows the user to turn on and off the Krakatoa Icon display in the viewport
  • The Size spinner next to the Icon checkbox is used to adjust the size of the PRT Loader's icon. The icon shows the Krakatoa Logo and can be used as a stand-in for selecting the loader when no particles are being displayed in the viewport. The Icon does not render so it is ok to be left visible most of the time.
  • [v1.0.1] Pressing the UPDATE VIEW CACHE button will invalidate the viewport cache. It is equivalent to moving the time slider or selecting a new viewport or rendering option that would require recaching the viewport particles. It can be used, for example, after changing a material property like the diffuse color to refresh the viewport color display without having to reselect the color mode from the drop-down list. The same button will also cause a refresh of the culling volumes, so if you added a new culling volume to the currently selected named selection set, you can press the button to update the particles display instead of reselecting the named selection set from the list.
  • [v1.1.0] The Names of the Render % and Limit spinners are now displayed by buttons. Pressing these buttons will show a context menu of typical values and allow the adding and removing of values to/from the list. This functions similar to the [>>] buttons in the Krakatoa GUI.

Culling and Deformations Rollout

Particle Culling

Please see the topic Particle Culling and Normals Acquisition for details and examples.

Modifier Gizmo Size

Deformation gizmos in 3ds Max are resized to fit the object's bounding box. Since the particle bounding box is constantly changing and might not even have the correct size when using Load First N Particles mode, the Particle Loader provides its own explicit and animatable modifier context size to any modifiers.

  • The Width, Length and Height values specify an explicit modifier context for any object space modifiers added to the Particle Loader. All values are animatable.
  • [v1.0.1] The Get buttons in front of the values can be used to get the corresponding value from the particle bounding box on the current frame. If the 3ds Max Auto Key option is enabled, the values will be keyframed.
  • [v1.0.1] The Get All From Object will set all three values at once. It can be used instead of pressing the 3 Get buttons one by one.

Please see the topic Particle Deformations for details and examples.

Particle Count Display

The Particle Count Display group of controls provides information about the status of the loader, the number of particles in the particle files, the particles scheduled for rendering and the count actually displayed in the viewport.

  • The Status Indicator in the upper left corner of the rollout can show 4 different colors depending on the status of the particle files on the current frame:
    • Gray- no particle files have been specified, nothing to show or render.
    • Green - all particle files were found and valid. Particles would render correctly.
    • Red - some particle files could be loaded. This would fail the rendering.
  • Clicking on the Status Indicator while it is red will display the last error message that caused the warning.
  • Checking the >View option will display the Viewport count in the viewport next to the one corner of the bounding box. In v1.0.x, the Disk and Render values could also be displayed in the viewport. To streamline the code and improve the display speed, these options were disabled in v1.1.0.
  • The View count value in the UI will show the requested viewport count while the value in the viewport will show the actual number of particles drawn, taking into account culling etc.
  • The text fields cannot be written into, but the values can be copied and pasted to/from the clipboard.
  • The Update Info button can be used to force a refresh of the info. It will also display the error message showing the last missing frame encountered if the status indicator is red.
  • The Graph area can be used to display information about the particle counts and missing frames similar to the ones displayed by the PRT Loader Analyzer Utility.

File Availability Graph

  • This mode is new in Krakatoa v1.1.0.
  • This mode collects data only about the existence of the files, not about their content. Thus it is much faster to process and display the data.
    • By default, the graph will be empty, only displaying a vertical dotted line representing the current frame.
    • Press the Update Graph button to collect data from the particle files in the loader.
    • The result is a set of horizontal stripes, one more than the number of file sequences in the PRT Loader.
    • The top stripe represents the total accumulated particle cloud.
      • Green represents frames that are available in all sequences.
      • Red represents frames where at least one sequence is missing a frame. Attempting to render that frame would cause an missing file error.
    • The following N stripes represent in color the file availability of each file sequence.
      • Green means that the frame is available AND all other sequences have that frame available.
      • Yellow means that the frame is available BUT at least one other sequence is missing the frame.
      • Red means that the frame is missing from that sequences.
      • Gray means that the Render flag of that sequence has been disabled and the sequence will not participate in the rendering (sort of "silent green")

Particle Count Graph

  • This is the original mode from Krakatoa v1.0.0.
    • By default, the graph will be empty, only displaying a vertical dotted line representing the current frame.
    • Press the Update Graph button to collect data from the particle files in the loader. NOTE that this can take a long time depending on the amount of files, frames and the location (network vs. local).
    • If the files are few and local, you can also check the >Auto option to refresh the graph display while changing timing and percentage values. WARNING: Use this at your own risk and only when the update time is short enough for interactive updates!
    • Note that the update time of the Graph in milliseconds will be reported in the status bar of 3ds Max.
    • The graph colors have the following meaning:
      • Green - all particle files were found and valid. Particles would render correctly. If displayed as a gradient, the count cannot be determined (CSV file sequences cannot report their count).
      • Red - If displayed as a red gradient, no particle files could be loaded and the renderer would fail. If displayed as solid red bar, some particles could be loaded but at least one file was missing, and it would fail the renderer.
  • [v1.0.1] A blue progress bar underneath the graph will represent the process of reading particle counts from all loaded sequences.

Don't Render Missing Files

  • This button performs a File Availability check and disables the Render Flag of all sequences that are missing at least one frame within the current scene range.

Presets

  • Any combination of custom settings can be stored to Preset Files for fast switching between typical modes.
  • Any saved preset can also be made the default preset to be applied when a new PRT Loader is created in the scene. Thus, if you like working with a specific percentage of particles, specific point size or color source, instead of changing the factory defaults after each PRT Loader creation, you can save your own factory defaults and whole libraries of favorite settings.
  • To create a new Preset,
  1. Set up your PRT Loader using all its settings (some settings are not saved though - like the file list and the Icon Size)
  2. Press the Save... button.
  3. A modal PRT Loader Preset Options dialog will open. Using Ctrl+Left Click, select/deselect the properties you want to be saved. You can also use the All, Invert and Default buttons to select all, invert the current selection or set the default selection.
  4. Enter a name for the preset in the Name field.
  5. Press SAVE PRESET to save or CANCEL to exit.
  • To load a preset, simply click on its name in the Presets listbox.
  • To delete a preset, select it from the list, then press Delete...
  • All presets are stored in the Krakatoa\Presets folder in your 3ds Max PlugCfg folder. To explore, copy, archive, delete manually etc. preset files, press the Explore... button - it will open a Windows Explorer at that folder's location.