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Overview

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

 

Parameters

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General

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Increase/Decrease resolution – Changes the resolution of the grid while maintaining its size. For more information, see the Grid Resolution example below.

 

 

 

Example: Scene Scale

 

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The following video provides examples to show the differences

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of Scene Scale

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 with values

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of 0.1, 5.0,

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and 15.0.

 

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Example: Grid Resolution

 

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The following video provides examples to show the differences when the Total cells from the Grid'

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Resolution

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 is at 570,000, 4,000,000,

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and 16,000,000.

 

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Boundary Conditions
Boundary Conditions

Container Walls

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X, Y, Z | x_bound, y_bound, z_bound – Select – Select between different boundary container wall conditions for the simulation grid.

Open – The simulation behaves fluid is allowed to leave the bounding box of the Simulator through this wall. If Fill Up for Ocean is enabled, the Wall is treated as if there is infinite fluid beyond the boundaryliquid below the Initial Fill Up level.
Jammed(-) – The simulation behaves as if there is a solid boundary in the negative direction. When Adaptive is enabled, the grid will not expand in this direction.
Jammed(+) – The simulation behaves as if there is a solid boundary in the positive direction. When Adaptive is enabled, the grid will not expand in this direction.
Jammed Both – The simulation behaves as if there is a solid boundary in both directions. When Adaptive is enabled, the grid will not expand in this direction.
Wrap  – The left and right boundaries are connected (toroidal topology). E.g. Fluid leaving the Simulator from the +X wall will enter it again from the -X wall.

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Confine Geom | usegridgizmo, gridgizmo – You can place here specify a closed geometry object with normals pointing outwards, and the simulation will run only inside this object. The rest of the cells will be frozen as if a solid body was covering them. This way you can fill irregular shapes with liquid, or generally speed up your simulation by chopping off empty cells when you have an irregular fluid shape, e.g. a rocket launch (this .

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While using a Confine Geometry can speed up a simulation, it will not reduce RAM usage

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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. Note that the   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

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  • one should be started only after the previous one has finished simulating.

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  • The Cascade Source parameter points to the previous simulator in the sequence.

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  • For the simulation to function correctly, you need to have

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  • the Velocity

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  • Grid Channeland all Particle Groups that are simulated in the Source

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  • Simulator exported to its cache files - otherwise the connection will not work properly.

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  • If you intend to use any additional channels such as RGB, particle

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  • IDs or

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  • Ages, etc, they also need to be exported from the Source simulator'

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  •  before running the current simulator

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Adaptive Grid

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Adaptive Grid

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 Either keep Adaptive Grid disabled or set the Container Walls: Z to  to Jammed Both when  when simulating Oceans.The  The Ocean Level parameter  parameter in the Rendering the Rendering rollout depends on the vertical size of your simulator.

Adaptive Grid | adaptiveAllows the The grid to will resize automatically during the simulation in order to prevent the liquid from leaving the LiquidSim box.bounds of the Simulator box. Note that only the Open Container Walls will expand and contract when Adaptive Grid is enabled.

Extra Margin | adapt_margin – Specifies the number of cells between the end of the grid and the active zone. You can use this to give the fluid a bit more room if the adaptive grid can't keep up with the adaptationsimulation.

No Smaller Than Initial Grid | nbigrid – When – When enabled, the adapting grid canthe Adaptive Grid can't contract to a smaller size than what is given as an the initial X,Y,Z size for the current frame. The given 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 not enableddisabled, the grid will always encompass only the active fluid and will move together with it if needed.

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Shrink to view | usegridfitcamera, grid_fit_cameraIf the camera rendering angle is known, you can limit the grid expansion up to the viewing frustum of the camera.Species a camera whose frustum will be used to determine the maximum expansion. The Adaptive Grid will not resize beyond the frustum. 

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 When a Shrink to view Camera is provided, the Adaptive Grid will expand no further than the already specified Maximum Expansion Limits.  

 

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