transport is easy
to set up with VCM
Fully Ray Traced Caustics
Use RenderMan's VCM integrator to create physically accurate caustic effects in a single pass ... without any baking or pre-passes. A notoriously difficult problem for path tracers, the VCM integrator combines bi-directional path tracing with transient photons to resolve caustics fast and efficiently.
The VCM integrator is not the solution for every scene, but the VCM integrator can deliver certain effects that path tracing just can't. This fundamental advantage of the RIS architecture offers maximum creative flexibility.
"Today Pixar launches the newest in that long line of innovations, a new rendering architecture known as RIS, that supports plug-in integrators and comes complete with a new industry standard path-tracer as well as a cutting-edge bidirectional path tracer.”