This page provides information on the Output rollout for a FireSmokeSim object.
The Output rollout holds the controls for the simulation result. When you start a simulation, the simulator will typically output an entire animation sequence, which is saved onto your hard drive by default. That sequence is saved as individual files, called caches, which contain raw simulation data for each timeline frame. The Output rollout lets you set the save path for the cache files, manage what data is written to those cache files, and determine their compression. Specifically, the cache data consists of grids and particles, which describe the fluid’s behavior. Grid Channels are written to each cache file, which represent the properties of the simulated fluid at that frame, such as Smoke, Temperature, Velocity, RGB and so forth. In the Output rollout, you can choose which Grid Channels to export to the cache files, based on your needs. The values for those exported channels will then be contained in each of the voxels in the simulation grid.
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UI Path: ||Select Fire Smoke Simulator object|| > Modify panel > Output rollout |
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Example: Fire/Smoke compression artifacts |
Backup Interval | backup – The frame interval between two backups of the full simulation state. You can later continue a stopped simulation from such frames (see the Restore button). To make a Restore possible at every frame, set this parameter to 1. A value of 0 means no backup frames will be exported. |
Compress Particles | prtcompress – Enables compression of the simulated particle systems when they are written to AUR cache files. VDB cache files exported from Phoenix do not support particle compression. Simulations with very high particle counts, such as 50 million or more, will produce large caches, so particle compression will help reduce the cache sizes significantly. If you are writing or reading the cache files over the network or to a disk drive, this could significantly speed up simulation and rendering. However, if you are writing the simulation caches to an SSD drive or other fast storage, and you can afford to have large cache files, then disabling the compression could actually speed up the simulation. |
Fluid properties are written inside Grid Channels. Here you can choose which Grid Channels will be exported to the cache files when running a simulation. Each channel stores a type of value, such as Temperature, Velocity, and so forth, with its own range of possible values that is most efficient for that specific channel type (see the Grid Channel Ranges). Phoenix determines the fluid’s behavior at a given time, based on the content of these Grid Channels. |
Note that the more channels are used, the slower the simulation runs and the larger the output files are. While scrolling the timeline, you can check which channels are present in the loaded cache file for the current frame, from the Cache File Content list in the Simulation rollout. |
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There are path environment variables in every OS, and they can be used with Phoenix cache file paths.
For example, to access environment variables in Windows 10 and Windows 8, follow these steps:
Using this, you can create a path (variable), give it a name, and use it for cache files in Phoenix.
For example, the path D:\PhoenixFD\Cache can be given the environment variable name "Cache". In the Phoenix Simulator Output rollout, you can specify the Output Path as the following:
$env(Cache)\cache_name###.aur
This will save the Phoenix cache files in D:\PhoenixFD\Cache.
Note that in order to reference environment variables, the following pattern must be used:
$env(<variable_name>)