I’ve tested RenderMan with spline rendering. it’s much faster compared with baked Geometry. the spline primitives are very good in Renderman.
I’ve stopped the test with mantra after 10 minutes, it is super slow even with optimized render settings.
the Renderman images rendered for 3:20 on a 6 core Xeon 2.7ghz with pxr pathtracer. 4k resolution
rendering splines directly saves a lot disk space and meshing time. interactive rendering was super responsive.
Octane 2019.2 renderings is very fast, I’ve used the geo to render it. 2 minutes, as except its lot faster the CPU renderings. the spline rendering in octane does features custom width yet.
Octane gives physical correct shading out of the box. Renderman the shading is extreme flexible with NPR renderings, which is hard to get in Octane. the IPR responsibility was a little slow with shader tweaks.
I’ve made a simple scene to test the physics of light. for proper light calculation, I used spectral render Indigo and Octane.
Indigo has multiple Engines, standard Spectral Path tracer on CPU or GPU and Bidirectional path tracing with MTL sampling (metropolis Light Transport). Octane has only default Spectral Path tracer on GPU but includes an MTL sampling method. I’v also added Renderman 23 to the test with its unified rendering integrator. It supports bidirectional path, manifold caustics and path guiding on the CPU.
Another render engine like Arnold or Cycles with regular Path tracing would impractical fro complex light calculation tasks.
The base scene is Sphere and squashed Sphere underneath inside a volume box (uniform VDB).
The following image is the result of Indigo Renderer with BiDirectional path tracing and MTL. It was by far the fastest rendering.