This required using a fork of Embree, newer LLVM version, unreleased ISPC
version and sse2neon directly from Git. Hopefully over time all the required
changes end up in official releases. For now we deviate from other platforms.
Based on contributions by Apple and Stefan Werner.
Ref D9527, D8237, T78710
embree marks a few of its functions with a dll_export macro
forcibly exporting these symbols from whatever binary links
them. Given we link embree statically and we do not want these
exports in the blender binary, the macro needs to be a no-op.
Note that this is turned off by default and must be enabled at build time with the CMake WITH_CYCLES_EMBREE flag.
Embree must be built as a static library with ray masking turned on, the `make deps` scripts have been updated accordingly.
There, Embree is off by default too and must be enabled with the WITH_EMBREE flag.
Using Embree allows for much faster rendering of deformation motion blur while reducing the memory footprint.
TODO: GPU implementation, deduplication of data, leveraging more of Embrees features (e.g. tessellation cache).
Differential Revision: https://developer.blender.org/D3682
