58be9708bf
Remove need for shadow caustic caster geometry to have a UV layout. UVs were useful to maintain a consistent tangent frame across the surface while performing the walk. A consistent tangent frame is necessary for rough surfaces where a normal offset encodes the sampled h, which should point towards the same direction across the mesh. In order to get a continuous surface parametrization without UVs, the technique described in this paper was implemented: "The Natural-Constraint Representation of the Path Space for Efficient Light Transport Simulation" (Supplementary Material), SIGGRAPH 2014. In addition to implementing this feature: * Shadow caustic casters without smooth normals are now ignored (triggered some refactoring and cleaning). * Hit point calculation was refactored using existing utils functions, simplifying the code. * The max number of solver iterations was reduced to 32, a solution is usually found by then. * Added generalized geometry term clamping (transfer matrix calculation can sometimes get unstable). * Add stop condition to Newton solver for more consistent CPU and GPU result. * Add support for multi scatter GGX refraction. Fixes T96990, T96991 Ref T94120 Differential Revision: https://developer.blender.org/D14623