Fluid Auto Resize attributes

Auto Resize

When on, Auto Resize dynamically resizes 2D and 3D fluid containers when the voxels near outer boundaries of the container have positive density. For example, 2D and 3D fluid containers expand or contract according to the current density of the fluid. As the fluid density dissipates in the simulation, the fluid boundary resizes to accommodate only positive fluid Density.

The smaller simulation area increases simulation speed, reduces rendered times, uses less memory, and results in smaller fluid cache files. See Dynamically resize a fluid container.

Resize Closed Boundaries

When on, fluid containers resize along the axis that have their respective Boundary attribute set to None, Both Sides, - Side, or Side. When off, fluid containers only resize along the axis that have their respective Boundary attribute set to None. Fluid containers do not resize along axis that have their Boundary attribute set to Wrap. See Boundary X, Y, Z and Change fluid behavior at the container boundaries.

Resize Closed Boundaries is on by default and only affects fluid containers when Auto Resize is on.

Resize To Emitter

When on, the fluid container uses the fluid emitter's position to set it's its offset and resolution in the scene. Turning on Resize To Emitter is useful in fluid effects with animated emitters as it ensures that the container moves and resizes to include the moving emitter. This means the emitter can be outside the fluid container at the start frame.

A Max Resolution attribute sets the outer resize boundaries. If the fluid has already expanded to the Max Resolution value, it will no longer expand to follow an emitter that moves outside of the fluid volume.

When Resize To Emitter is on, the fluid container jumps and contracts to emission regions in a single step. When Resize To Emitter is off, the container resizes one voxel per frame.

Note: You can turn on Resize in Substeps to resize the container each Substep.
Resize In Substeps
When on, auto resized fluid containers resize each substep. When Resize In Substeps is off, fluids only resize one voxel per simulation step.
Note: Collision boundaries are evaluated per substep only when Auto Resize and Resize In Substeps are on.
Max Resolution

Specifies the average maximum resolution per side that a fluid container resizes when Resize to Emitter is on.

For example, if Max Resolution is set to 10, then the total resolution of the fluid cannot be greater than that of a 10×10×10 fluid. This means that you can have a 3D fluid with a Resolution of 5×20×10, but not 6×20×10, or you can have a 2D fluid with a Resolution of 20×50, but not 21×50.

Dynamic Offset

Displays the local space translation of the fluid that is computed when Auto Resize is on. Maya either sets the values during fluid auto resizing, or reads them from fluid nCache files.

Auto Resize Threshold

When Auto Resize is on, Auto Resize Threshold sets the density threshold value that causes the fluid container to resize. Auto Resize Threshold uses the current Density value in the second row of voxels from the containers edge to determine the outer boundaries of the fluid, then resizes the fluid container accordingly. As you increase the threshold value, the fluid Density at the container boundaries increases.

See Dynamically resize a fluid container.

Auto Resize Margin

Specifies the number of empty voxels added between the fluid container boundary and regions of positive density in the fluid. Auto Resize Margin lets fluids flow more naturally near auto- resized boundaries and is useful for fast-moving and low density fluids. Auto Resize Margin does not affect the way Auto Resize Threshold resizes the fluid container.

When using Auto Resize Margin with fast flowing fluids, use low Substep values.