Fix bug: don't compute ray differentials for specular reflection/transmission if the incident ray doesn't have ray differentials itself.
Fix bug: don't compute ray differentials for specular reflection/transmission
if the incident ray doesn't have ray differentials itself.
patwonder/pbrt-v2-skin,patwonder/pbrt-v2-skin,patwonder/pbrt-v2-skin,patwonder/pbrt-v2-skin,patwonder/pbrt-v2-skin