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The PhoenixFDSimulator works best when the scale of the container matches the real-world size of the simulated effect. For example, If you are simulating a camp fire, your container should be at most a couple of meters wide. Note that it doesn't matter if this is two meters or two thousand millimeters - the way you view the units is irrelevant. Phoenix always converts the units to a common world-size length, so the only important thing is the size of the container. If you are simulating a volcano for example, the container should be several hundred meters wide, or several hundred thousand millimeters.

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If your scene is structured in a way that makes it hard for you to scale the objects to their real-world size, you can use the Scene Scale parameter to tell Phoenix FD to treat the container as larger / smaller than it actually is when measured in Scene Units. This will influence the dynamics of the simulation, allowing to you achieve the correct behavior for your simulation without the need to tweak the size of the objects in your scene.

Using the parameters on this roll-out you can:

  • Specify the Size and Resolution of the Simulator
  • Enable / Disable Adaptive Grid which is a performance optimization allowing you to keep the size of the Simulator as small as possible thus reducing RAM usage
  • Specify which Walls of the Simulator will be considered Open (infinite) or Jammed (ie. as solid obstacles, closed)
  • Link multiple Simulators in a Cascade setup - for more information, please check the following article: Transferring fluid between Simulators using a Cascade Connection.
  • Specify a Confine Geometry to limit the fluid calculations only to the volume of the specified object


Cell size | cellsz – The size of a single voxel, in scene units. For more information, see the Grid Resolution example below.

X, Y, Z | xc, yc, zcThe grid size in cells. The dimensions shown next to XYZinclude the are the grid sizes in the scene, multiplied by the Scene Scale parameter  parameter - these sizes show how big the container would be for the simulation. In the solver will see the grid box and you can use the Scene Scale to cheat the solver into simulating as if the grid box was larger or smaller. In case you want to see how big the container for the loaded cache is in the scene without accounting for the Scene Scale, see the Container Dimensions in the Simulation rollout.


Cascade Source | usecascade, cascade  – Specifies the source LiquidSim to connect this simulator to, forming a cascading simulation. This allows you to join several simulators into a structure with a complex shape. This can help you reduce memory usage by using many smaller simulators in place of a single large simulator.  For more information, see the Connecting Two Simulators in a Cascade Setup section on the Tips and Tricks page.

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  • The simulators must be run sequentially and each one should be started only after the previous one has finished simulating. The Cascade Source parameter points to the previous simulator in the sequence.
  • For the simulation to function correctly, you need to have the Velocity Grid Channel and all Particle Groups that are simulated in the Source Simulator exported to its cache files - otherwise the connection will not work properly.
  • If you intend to use any additional channels such as RGB, particle IDs or Ages, etc, they also need to be exported from the Source simulator's Output rollout before running the current simulator


No Smaller Than Initial Grid | nbigrid – When enabled, the Adaptive Grid can't contract to a smaller size than what is given as the initial X,Y,Z size for the Simulator. Note that this way the initial grid box is always included, even if the fluid has moved farther from it. If this option is disabled, the grid will always encompass only the active fluid and will move together with it if needed.

Expand and Don't Shrink onlyexpand – When enabled the Adaptive Grid will expand without shrinking. 

Maximum expansion | maxexp, expx/y/z/neg/pos – Specifies maximum growth sizes for each side of the grid, in cells. Using this, you can stop the expansion in certain directions.