• Added quaternion motion blur for correct interpolation of rotational transformations.
• Fixed wrong bounding calculations when a motion blurred instance di
  instantiate a motion blurred scene.
• In robust mode the depth test consistently uses tnear <= t <= tfar now in order
  to robustly continue traversal at a previous hit point
  in a way that guarentees reaching all hits, even hits at the same place.
• Fixed depth test in robust mode to be precise at tnear and tfar.
• Added next_hit tutorial to demonstrate robustly collecting all hits
  along a ray using multiple ray queries.
• Implemented robust mode for curves. This has a small performance impact but
  fixes bounding problems with flat curves.
• Implemented issue with motion blur builder where number of time segments
  for SAH heuristic were counted wrong due to some numerical issues.
• Fixed an accuracy issue with rendering very short fat curves.
• rtcCommitScene can now get called during rendering from multiple threads
  to lazily build geometry. When TBB is used this causes a much lower overhead
  than using rtcJoinCommitScene.
• Geometries can now get attached to multiple scenes at the same time, which
  simplifies mapping general scene graphs to API.
• Updated to TBB 2019.9 for release builds.
• Fixed a bug in the BVH builder for Grid geometries.
• Added macOS Catalina support to Embree releases.