All Rix plugins are descendants of this class.

Describe various conventions that are shared amonst RixBxdf, RixIntegrator, RixProjection etc.

Must describe InstanceData.

RixParameterList

important class! must describe EvalParam and how classes use it!

RixShadingContext

even more important class!

numPts

scTraits

integratorCtxIndex, rayId, etc etc

GetBuiltinVar: why

GetPrimVar: why

EvalParam: how to pull on upstream pattern nodes

when to SetBuiltinVar

GetNearestHits: when to trace rays

Memory allocation