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The Input rollout determines the path of the input files for rendering and preview, as well as the playback effects. Note that some playback settings require a fractional input frame, in which case the frame is blended between the previous and the next one.

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To set up rendering and simulation cache paths manually, see Chaning the Default Phoenix Paths in the Tips and Tricks page.

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UI Path: ||Select Liquid Simulator | LiquidSim object|| > Modify panel > Input rollout

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Parameters

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CachePath
CachePath
Preview & Render Cache Path | rendinput – Gives the directory and the name template for the input files. The default is $(same_as_output). Use the button to select the path or type it manually. Phoenix has some keywords that can be used for more flexibility:

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$(same_as_output) [nodeName] – The same path that is set in the Output rollout would be used for loading the preview and render caches. When a node name is specified, its output is passed to the current input.
$(simoutput) – A synonym for $(same_as_output).
$(dir) – The scene directory.
$(scene) – The scene file name.
$(handle) – A unique number of the node.
$(nodename) – The name of the node.
$env(<variable_name>) – An environment variable. See Using Environment Variables.

signs can be used to specify the cache frame number with at least as many digits as the pound signs. If the number of frame digits is less than the number of pound signs, the number is padded with zeroes to the left. For example:

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11010001
1010100010
1000100010001000
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The default rendering settings are tuned to Phoenix FD simulations, and they might not work well for imported 3rd party cache files.
This is why when loading OpenVDB or Field3D files generated by other software packages, you are given the option to choose a preset. The presets will change the render settings to reasonable default values. The presets will also modify the orientation of the cache files depending on the coordinate system of the source application (Y-up versus Z-up) by Enabling / Disabling the Flip Up Axis option.
You can further edit the parameters in the Rendering rollout to achieve the desired appearance of your simulation.

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You can suppress showing of the dialogues offering presets using the inDontOfferPresets attribute of the Simulator. Setting inDontOfferPresets to 1, as shown in the image below, will disable the presets pop-up window displayed when a VDB or Field3D cache files are loaded.

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Clicking the "..." button will open a menu with the following options:

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Default

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With .f3d or .vdb cache loaded

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Browse – Opens a dialog for choosing one of several cache file types. Phoenix FD can import *.f3d and *.vdb files from other fluid simulator software products. See How to import and render simulations from FumeFX, Houdini and Maya.

  • Phoenix FD *.aur 
  • Field3D*.f3d
  • OpenVDB*.vdb

Reset to Default – Resets the cache path to the default value of $(same_as_output).

Show File Name... – Evaluates the full disk path provided to the Simulation Cache Save Path parameter.

3rd Party Channel Mappings... – This option is available when a .f3d or .vdb cache is loaded. It launches the Channel Mappings dialog for mapping 3rd party cache channels. See the Channel Mappings section below for more information.

Help - Opens this Help page.

 

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This section contains playback options you can use for retiming a simulation after it has already finished. Using these, you can speed up, slow down or animate the motion of the simulated sequence. When retiming an existing simulation from this section without re-simulating, additional RAM might be used, and loading a new timeline frame may take longer when the frame must be obtained by creating a new one between two adjacent cache files. We will refer to the process of creating an intermediate frame from two caches as Blending. Some of the settings in this section might require specific grid or particle channels to be saved to the cache files during simulation from the Output rollout.

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 In order to blend particles, you must enable the export of the Particle ID channel from the Output rollout of the simulator.

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Interpolation – Simple linear interpolation suitable for slow simulations. This is the fastest method but it does not capture movement well and may produce flickering.
Velocity – Velocity-based interpolation. Produces better results, but works more slowly. Captures well the movement of the fronts of the plumes, but does not work well for smoke moving backwards, and also may produce flickering. It  requires an exported grid velocity channel from the Output rollout.
Precise Tracing - Improved Velocity based interpolation for Fire and Smoke simulations. Captures fire/smoke plume movement very well and can handle very low Play Speeds. Requires an exported grid Velocity channel, as well as Advection Origin channel from the Output rollout.

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Frame Blending is better suited for simulations without much variety in velocity. For more chaotic simulations, it is better to run a Resimulation using Time Bend controls. Time Bend Resimulation will calculate a better intermediate result for each frame and store it in new cache files that can later be loaded faster, as opposed to Frame Blending which re-launches every time the timeline frame changes. However, for very slow moving simulation the Precise Tracing method produces better looking results than Time Bend Resimulation. For more information, see How to slow down a simulation, animate the time-scale, etc.

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Example: Timeline Origin

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The following example demonstrates how the Timeline Origin parameter can be used to specify which frame on the timeline is treated as the first frame when reading the Input Path cache files.

The files go from simulationFrame_000 to simulationFrame_030. When the Timeline Origin is set to 10, they are read as if they were saved as simulationFrame_010 to simulationFrame_040.

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Example: Cache Origin and Play Speed

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The following example demonstrates how the Cache Origin and Play Speed can be used to offset and speed up the input cache files.

The files go from simulationFrame_000 to simulationFrame_030. When the Timeline Origin is set to 100, they are read as if they were saved as simulationFrame_100 to simulationFrame_130.

The Cache Origin is then used to specify which simulationFrame simulation Frame will be placed on Timeline Origin = 100. Because Cache Origin is set to 10, the whole sequence is shifted 10 frames back such that simulationFrame_000 is placed at frame 90. Thus, the sequence now goes from frame 90 to frame 120.

The Play Speed is then set to 2.0. Those thirty frames are now reduced to fifteen. The Cache Origin frame is treated as the middle point when shrinking the sequence.

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Example: Looping a Simulation

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The following example demonstrates how the Input rollout parameters can be used to loop a simulation.

The Timeline Origin parameter is set to 0 - this will be the first frame of the timeline which the Input Path files read into the scene by the Simulator will be placed on.

The Cache Origin is set to 10 so simulationFrame_010 will be read and placed at Timeline Origin = 0.

The Play Length is set to 15 so the sequence now repeats itself every 15 frames when played back (those are actually simulationFrame_010 to simulationFrame_025).

Finally, the Loop Overlap parameter is set to 5 to provide a few extra frames for blending the start and end of the loop together in a smooth transition.

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Grid Channel Smoothing

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Grid Smoothing is performed after the cache file is loaded for the current frame, so for large grids it could cause significant lag after changing frames. To prevent this from occurring, switch it off during the design process and re-enable it again before rendering.

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Different applications use different channels and might have different names for them. When loading f3d/vdb files, Phoenix tries to automatically make the conversion to the supported channels. If a channel is not mapped by default, a channel can be manually set from the dropdown menu. It can be accessed from the Cache Path menu when a 3rd party cache is loaded (e.g. .f3d or .vdb files).

 
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All mappings are kept in a single string parameter, accessible by the name "usrchmap". An example mapping string is:

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