Enabling it on any other configurations will lead to render non physically correct caustics. Refractive Caustics should only be activated when Shadow Casting Mode is set to Opaque (when Opacity is set to 1,1,1), Physical or Artistic with Shadow Opacity at 100% and Shadow Color set to 0%. This is very important for the path tracer since depending on the material and the expected behavior, double sidedness can't be always assumed. Shading normals follow the ones defined by the primitive. By default materials are considered as single sided surfaces. It is possible to specify the sidedness of a material. For example, this can be used to disable multiple scattering on volumes or on the contrary, used to increase the number of bounces when simulating clouds.

This is very handy, when you need to increase samples on specific materials while keeping others being sampled by the value defined in the path tracer. It is possible to override all material sampling settings directly at the material level instead of using the ones defined by the path tracer. Most materials share a set of predefined attributes to control the sampling and the geometry approximation. All materials can be connected to a network of textures to drive their physical attributes but also be combined in layers and blended together to accurately approximate real world materials while keeping rendering performance high. Some are specialized for hair rendering or simulating specific types of materials, while some others can be of general use.

Clarisse built-in path tracer provides a set of physical materials which react realistically to lights.

Blending materials isotropix clarisse