Houdini 20.5 Nodes VOP nodes

Volume Sample VOP node

Samples the value of a volume primitive stored in a disk file.

Samples a specific volume primitive. Returns 0 if primnum is out of range, the filename is invalid, or the given primitive is not a volume primitive.

Using volumesample() functions on points outside of a volume box will extend the sign distance field if the volume boundary is SDF. The distance to the bounding box is added to the streaked bounding box value.

The following diagram shows how the SDF extension works.

Boundary values

  • Constant values mean there is a value that all outside samples are set to (usually 0). So even if the border voxel is 1, as soon as you peak outside it is 0.

  • Streak means the boundary value is held into the surrounding area. So an out-of-bound sample is clamped to the volume and the value samples. This means a value of 1 at the boundary will streak into the surrounding space.

  • Repeat means space is tiled with the volume.

See also

VOP nodes