Use MTLPatchShaderSource to provide the patch basis shader source on
all Apple platforms. The immediate advantage of this change is ability
to use GPU subdivision on iOS. Another advantage is that it moves us
further away from frameworks which got deprecated by Apple and it might
save us some headache in the future.
Also tweak backend-specific defines to match definitions from OpenSubdiv.
The annoying difference is that OSD_PATCH_BASIS_METAL is defined by the
OpenSubdiv as 1 in the very beginning of the base code, which is not done
for the OSD_PATCH_BASIS_GLSL is not defined by the OpenSubdiv at all.
Ref #143445
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TODO:
- [X] Check it works correctly on macOS
- [x] Check it works correctly on Linux
Pull Request: https://projects.blender.org/blender/blender/pulls/143462
07bf1bd87b