The Volume SDF operation rebuilds a signed distance field from a given isocontour in a volume. The new SDF is the same resolution as the original volume.
This can be used to turn a fog volume into an SDF to get fast distance computations. It can also be used to renormalize a signed distance field that has been stretched away from its ideal shape.
The boundary condition of the volume will be changed to SDF by this SOP. To change it to constant or streak, use the Primitive SOP.
This node currently only works with standard Houdini volumes. It does not work with VDBs.
The volume primitives to be used.
The iso contour to rebuild on. This will become the 0 contour of the new SDF. For fog volumes 0.5 is good. For SDF sources, 0 is usually good.
Invert the sense of the generated SDF. By default the sign of the SDF will match the original, so higher values in the original are higher values in the result. However, with fog volumes, you likely want the opposite so the white areas of fog become negative, hence inside.
Use Maximum Distance
Stops the conversion when a certain distance from the isocontour is reached. This is very useful if you only care about a certain band around the surface as it can avoid computing the value for the rest of the voxels.
Distance in object space to compute. Voxels farther than this distance will be clamped to +/- this distance.