The Manifold Walk option in PxrUnified makes use of a technique to generate caustics that can be less expensive than generating photons through the scene. It also excels when using small light sources. You can also fine tune what is and isn't a receiving or caustic generating material. This is especially useful for eyes in VFX and Feature Animation work. You can selectively have the cornea trace caustics onto the iris of the eye adding realism and beauty. You can also better illuminate objects realistically behind or inside transmissive objects.

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