Embree

- Added support for motion blur time range per geometry. This way geometries
can appear and disappear during the camera shutter and time steps do not have
to start and end at camera shutter interval boundaries.
- Fixed crash with pathtracer when using --triangle-sphere command line.
- Fixed crash with pathtracer when using --shader ao command line.
- Fixed tutorials showing a black window on macOS 10.14 until moved.

- Fixed compile issues with ICC 2019.
- Released ZIP files for Windows are now provided in a
version linked against Visual Studio 2013 and Visual Studio 2015.

- Fixed crash when using curves with RTC_SCENE_FLAG_DYNAMIC
combined with RTC_BUILD_QUALITY_MEDIUM.

- Fixed intersection distance for unnormalized rays with line segments.
- Removed libmmd.dll dependency in release builds for Windows.
- Fixed detection of AppleClang compiler under MacOSX.

- Bugfix in flat mode for hermite curves.
- Added EMBREE_CURVE_SELF_INTERSECTION_AVOIDANCE_FACTOR cmake option to
control self intersection avoidance for flat curves.
- Performance fix when instantiating motion blurred scenes. The application
should best use two (or more) time steps for an instance that instantiates
a motion blurred scene.
- Fixed AVX512 compile issue with GCC 6.1.1.
- Fixed performance issue with rtcGetGeometryUserData when used
during rendering.
- Bugfix in length of derivatives for grid geometry.
- Added BVH8 support for motion blurred curves and lines. For some workloads
this increases performance by up to 7%.
- Fixed rtcGetGeometryTransform to return the local to world transform.
- Fixed bug in multi segment motion blur that caused missing of perfectly
axis aligned geometry.
- Reduced memory consumption of small scenes by 4x.
- Reduced temporal storage of grid builder.

- Improved watertightness of robust mode.
- Line segments, and other curves are now all contained in a single
BVH which improves performance when these are both used in a scene.
- Performance improvement of up to 20% for line segments.
- Bugfix to Embree2 to Embree3 conversion script.
- Added support for Hermite curve basis.
- Semantics of normal buffer for normal oriented curves has
changed to simplify usage. Please see documentation for details.
- Using GLFW and imgui in tutorials.
- Fixed floating point exception in static variable initialization.
- Fixed invalid memory access in rtcGetGeometryTransform for non-motion
blur instances.
- Improved self intersection avoidance for flat curves. Transparency rays
with tnear set to previous hit distance do not need curve radius
based self intersection avoidance as same hit is calculated again. For this
reason self intersection avoidance is now only applied to ray origin.