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This page provides information on the Grid rollout for a LiquidSim object.


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The parameters in this rollout control the size and resolution of the grid.



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




Scene Scale | scenescale – Specifies a multiplier for the original scene units of the scene. Phoenix FD works best when the container size is close to the real-world size of the desired effect. You can use this parameter to make the simulator see the container as bigger or smaller than it actually is in the scene, in case you cannot change the general scene units of 3ds Max. Check the labels to the right of XYZ for the container sizes affected by this parameter. Bigger scale would make the fluid move more slowly because it needs to travel a greater distance, while smaller scale makes the fluid move faster and more chaotic. For more information on how changing the Scene Scale affects the simulation, see the Scene Scale example below.

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, zc – The grid size in cells. The dimensions shown next to XYZ include the Scene Scale parameter - these sizes show how big the container would be for the simulation. 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.

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


The following video provides examples to show the differences of Scene Scale with values of 0.1, 5.0, and 15.0.





Example: Grid Resolution


The following video provides examples to show the differences when the Total cells from the Grid's Resolution is at 570,000, 4,000,000, and 16,000,000.




Container Walls

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

Open – The simulation behaves as if there is infinite fluid beyond the boundary.
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).

Confine Geom | usegridgizmo, gridgizmo – You can place here 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 will not reduce RAM usage though).

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 simulators must be run sequentially and each next one should be started only after the previous one has finished simulating. The Cascade Source parameter points to the previous simulator in the sequence. Also, note that for the simulation to function correctly, you need to have exported to cache the Velocity channel of the grid and of all the particle groups that are simulated in the Source simulator, otherwise the connection will not work properly. Additionally, 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.


Adaptive Grid

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

Adaptive Grid | adaptive – Allows the grid to resize automatically during the simulation in order to prevent the liquid from leaving the LiquidSim box.

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 adaptation.

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

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.

Shrink to view | usegridfitcamera, grid_fit_camera – If the camera rendering angle is known, you can limit the grid expansion up to the viewing frustum of the camera.