Trace Set - Arnold for Houdini

It is possible to designate objects to be part of one or many trace sets. The trace_set shader marks specific rays with an inclusive or exclusive trace set.

With the Arnold Visibility Geometry Properties, it is possible to tag objects to be part of one or many trace sets.

Example

Below is a shading network for a floor material which segregates shadow and specular rays into two different trace sets:

The sphere objects are then tagged to be part of the shadows, specular, or both trace sets: