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A VDB grid is a sparse tree representation of voxel data. For instance, a float grid stores one single-precision floating point value per voxel. After the OpenVDB file is loaded, a list of grid names become available in the pulldown menu. Pick the grid name you want to sample. All grids are sent to the renderer as primvars, however only those wired into the PxrVolume shader will be used.
Filter Width
If set to 0, this disables mipmapping. If greater than 0, values less than 1 bias towards finer levels of the mipmap and values larger than 1 bias towards coarser levels.
Density Multiplier
Scales the values in the density grid of the volume. This should be more efficient than scaling the density in the PxrVolume shader.
Density Rolloff
Values greater than 0 produce a logarithmic falloff in density values. Smaller rolloff values produce greater falloff.
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Blobbies are currently not supported by the PrmanVolume node. |
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RfK will internally create primvars for all grids found in the VDB file (float or vector3). There is no penalty if they are not used. PxrVolume can look up the density and velocity primvars by name. For accessing To access other primvars or to modify the existing density and velocity, primvars can also be accessed by the shading network via the PxrPrimvar pattern node:
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