Embree

- Added linear cone curve geometry support. In this mode a real geometric surface for curves
with linear basis is rendered using capped cones. They are discontinuous at edge boundaries.
- Enabled fast two level builder for instances when low quality build is requested.
- Bugfix for BVH build when geometries got disabled.
- Added EMBREE_BACKFACE_CULLING_CURVES cmake option. This allows for a cheaper round
linear curve intersection when correct internal tracking and back hits are not required.
The new cmake option defaults to OFF.
- User geometries with invalid bounds with lower>upper in some dimension will be ignored.
- Increased robustness for grid interpolation code and fixed returned out of range u/v
coordinates for grid primitive.
- Fixed handling of motion blur time range for sphere, discs, and oriented disc geometries.
- Fixed missing model data in releases.
- Ensure compatibility to newer versions of Intel® oneTBB.
- Motion blur BVH nodes no longer store NaN values.

- Round linear curves now automatically check for the existence of left and right
connected segments if the flags buffer is empty. Left segments exist if the
segment(id-1) + 1 == segment(id) and similarly for right segments.
- Implemented the min-width feature for curves and points, which allows to increase the
radius in a distance dependent way, such that the curve or points thickness is n pixels wide.
- Round linear curves are closed now also at their start.
- Embree no longer supports Visual Studio 2013 starting with this release.
- Bugfix in subdivision tessellation level assignment for non-quad base primitives
- Small meshes are directly added to top level build phase of two-level builder to reduce memory consumption.
- Enabled fast two level builder for user geometries when low quality build is requested.

- Added EMBREE_COMPACT_POLYS CMake option which enables double indexed triangle and quad
leaves to reduce memory consumption in compact mode by an additional 40% at about
15% performance impact. This new mode is disabled by default.
- Compile fix for Intel® oneTBB 2021.1-beta05

- Added round linear curve geometry support. In this mode a real geometric surface for curves
with linear basis is rendered using capped cones with spherical filling between
the curve segments.
- Added rtcGetSceneDevice API function, that returns the device a scene got created in.
- Improved performance of round curve rendering by up to 1.8x.
- Bugfix to sphere intersection filter invocation for back hit.
- Fixed wrong assertion that triggered for invalid curves which anyway get filtered out.
- RelWithDebInfo mode no longer enables assertions.
- Fixed an issue in FindTBB.cmake that caused compile error with Debug build under Linux.
- Embree releases no longer provide RPMs for Linux. Please use the RPMs coming with the package
manager of your Linux distribution.

- Added collision detection support for user geometries (see rtcCollide API function)
- Passing geomID to user geometry callbacks.
- Bugfix in AVX512VL codepath for rtcIntersect1
- For sphere geometries the intersection filter gets now invoked for
front and back hit.
- Fixed some bugs for quaternion motion blur.
- RTCRayQueryContext always non-const in Embree API
- Made RTCHit aligned to 16 bytes in Embree API

- Added quaternion motion blur for correct interpolation of rotational transformations.
- Fixed wrong bounding calculations when a motion blurred instance did
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 guarantees 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.
- Improved quality of motion blur BVH by using linear bounds during binning.
- 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 Intel® 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 Intel® TBB 2019.9 for release builds.
- Fixed a bug in the BVH builder for Grid geometries.
- Added macOS Catalina support to Embree releases.