Primitive Variables (commonly known as 'primvars') are pieces of data associated with geometry. These are particularly useful for shaders that need to access custom data from the geometry.

An example scene file can be downloaded here.

Solaris specific information:

• The SOP Create and SOP Import LOPS automatically create custom primvars on the imported geometry.
• Arnold can query these via the user data shader nodes.
• For built-in primvars, use the utility shader shader.