This enables the new quaternion interpolation
in Embree 3.7.0 and makes motion blur results
match 1:1 with Cycles' own BVH.
Nice! Great that Embree added support for it.
I assume some Linux distros might be unhappy about going straight to the latest version as a minimum, but meh, Embree isn't on by default anyways.
Code seems fine generally, just one question.
I assume that Embree does the proper slerp, so we can't take this shortcut anymore?
Embree does proper slerp, and Mixing Embree’s slerp for intersections and nlerp for intersection refinement was causing self-shadowing.
Switching Cycles from nlerp to slerp i was unable to measure a performance difference. I will do some more testing though.