i am testing the different integrators of Renderman 23 in Houdini. the limit was 2 minutes render time on a 6 core Xeon, one HDRI dome light. Alembic geo 1.7 GB file.
direct lighting vs Pathtracer (below)
pxr unified vs pxr unified bidirectional (below)
pxr bi directional path guiding vs pxr vcm (below)
the shader settings for pxr unified integrator need to be adjusted to match the look. it took 30 seconds for the first pixel. the interactive responds time is excellent . the clamped highlights comes the buggy Houdini 18.0.287, below some scene with Houdini 18.0.237
Renderman 23 CPU vs Arnold 6 GPU (below)
the reflection differences come from normals, Arnold calculates it’s on normals, Renderman took the normals from the Geometry. i’ve tried with Karma but i had issues and crashes with it.