Cycles: Re-added runtime checks for the correct Embree build.

Merge branch 'master' of git.blender.org:blender into cycles_embree

Cycles: Set the preprocessor flag to tell Embree it's using a static library.

Cycles: Some cleanup for Embree integration.

Cycles: Embree option is now only visible when Cycles was compiled with Embree.

build_deps: Made sure Embree is being found on case sensitive file systems.

Embree: Set max ISA to AVX2 to get consistent builds across compilers.

Cycles: Added Embree to `make deps` script and changed CMake build files to find and fetch static Embree libs from the build location.

Cycles: Made things compile with Embree disabled.

Cycles: Turn the Embree build setting off by default.

Merge branch 'master' of git.blender.org:blender into cycles_embree

# Conflicts:
# build_files/cmake/platform/platform_win32.cmake

Merge branch 'master' of git.blender.org:blender into cycles_embree

Cycles: Fixed some warnings.

Merge branch 'cycles_embree' of git.blender.org:blender into cycles_embree

Cycles: Laid some foundation for embree ray accelerator: flags, UI and CMake

Cycles: more work on embree integration - triangle meshes now support deformation motion blur

Cycles: Progress with embree integration, still incomplete however

Cycles: Embree accelerator now supports instanced triangle meshes

Cycles: Embree support for ribbon line segments and subsurface scattering

Cycles: Added volume support for embree

Cycles: added memory and progress callbacks to embree

Cycles: embree hair now uses curve and not line segments, no more intersection filters for closest hit queries

Cycles: improvements to hair rendering using embree

Cycles: Added support for BVH refitting/dynamic meshes with embree

Cycles: improved defaults for embree option, enable embree in the UI only when a CPU device is selected

Cycles: prevented interactive rendering from crashing with Embree when objects are made invisible - RTCScenes now only get deleted by the top level BVH

Cycles: fixed some warnings in embree integration

Cycles: fixed Windows build with Embree

Cycles: Added Embree to Unix CMake files

Cycles: fixed Embree transparent shadow ray intersection to terminate properly when opaque objects are hit

Cycles: Added runtime checks for Embree build. If Embree is not configured correctly, it will print warnings to the console.

Cycles: Fixed parametric coordinates for hair intersections with Embree

Cycles: Extended Embree integration

Implemented ribbon curves and thick curves for hair.
Embree now obeys the static/dynamic BVH setting.

Cycles: removed use of constexpr to stay compatible with pre-C++11 compilers

Cycles: Set the compact flag on Embree to save memory

Cycles: Fixed wrong Embree line intersections

Line segments should not go through the backfacing test.

Cycles: Code style cleanup

Cycles: Fixed a crash when setting up Embree hair curves

Cycles: Fixed Embree Volume rendering when the camera is inside a volume

Cycles: Matched motion interpolation to Embree's interpolation

When Embree is turned on, the transform matrices of motion steps are now interpolated linearly (the wrong way). Cycles itself has a better way of interpolating, but when mixing it with Embree's direct matrix interpolation, it results in artefacts.

Cycles: Removed scaling from Embree's object motion blur.

Cycles native drops scaling from motion interpolation, the scale of the center of the frame gets reused to all motion positions. Embree could interpolate scaling too, but mixing the two then causes trouble with secondary rays, as Cycles does its own transformation interpolation in the intersection refinement. For now, restrict Embree to the common denominator, hopefully soon we can reintroduce scaling motion blur to Cycles.

Revert "Cycles: Removed scaling from Embree's object motion blur."

This reverts commit 3194e05d3f27124924f81b70400fb45fe022d9e4.

Merge branch 'master' of git.blender.org:blender into cycles_embree

# Conflicts:
# intern/cycles/bvh/bvh.cpp
# intern/cycles/device/device.cpp
# intern/cycles/device/device.h
# intern/cycles/device/device_cpu.cpp
# intern/cycles/kernel/geom/geom_object.h
# intern/cycles/render/mesh.cpp
# intern/cycles/render/scene.h

Merge branch 'master' of git.blender.org:blender into cycles_embree

Merge branch 'master' of git.blender.org:blender into cycles_embree

Merge branch 'master' of git.blender.org:blender into cycles_embree

Merge branch 'cycles_embree' of git.blender.org:blender into cycles_embree

Merge branch 'master' of git.blender.org:blender into cycles_embree

# Conflicts:
# intern/cycles/blender/addon/properties.py

Cycles: Updated Embree integration to version 3.2

Cycles: Raised thread stack size to 1MB for macOS to be consistent with Windows.

Embree BVH builds would run out of stack space in the default of 512kB.
This means macOS builds have to stay with pthreads and can't use std::thread.

Revert "Cycles: Raised thread stack size to 1MB for macOS to be consistent with Windows."

This reverts commit 151b5a9a1e568476c6886709b460edbf0936f7f7.

Set thread stack size on macOS to 1MB for Embree builds.

Merge branch 'master' of git.blender.org:blender into cycles_embree

Cycles: Fixes for transparent shadows and SSS when using Embree.

Cycles: Small fixes for Embree.

Cycles: Code formatting in Embree integration.

Cycles: Switched Embree curves to Hermite basis. Unforunately, Embree 3.2.0 has a bug with Hermite basis ribbons, so those won't render correctly at the moment.

Cycles: Improved stability with Embree memory callback

Cycles: Code style fixes for Embree, removing some unused data.

Cycles: Some more cleanup in Embree integration, added intersection filter to do backfacing hair correctly.

Merge branch 'master' of git.blender.org:blender into cycles_embree

# Conflicts:
# intern/cycles/blender/blender_sync.cpp
# intern/cycles/bvh/bvh.cpp
# intern/cycles/device/device_cpu.cpp
# intern/cycles/kernel/kernel_types.h

Cycles: Embree now traverses only the object subtree for local intersection tests.

Cycles: Some cleanup of Embree integration.

Cycles: Some style fixes for Embree integration.

Cycles: Some more cleanup/commenting for Embree integration.

Differential Revision: https://developer.blender.org/D3682

Cycles: Some more cleanup/commenting for Embree integration.

Cycles: Some style fixes for Embree integration.

Cycles: Some cleanup of Embree integration.

Cycles: Embree now traverses only the object subtree for local intersection tests.

Merge branch 'master' of git.blender.org:blender into cycles_embree

# Conflicts:
# intern/cycles/blender/blender_sync.cpp
# intern/cycles/bvh/bvh.cpp
# intern/cycles/device/device_cpu.cpp
# intern/cycles/kernel/kernel_types.h