Blender Git Loki

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

Cycles: Added NULL pointer check

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

making things build on Linux

Cycles: Added texture differentials to mesh light sampling. Currently based on purely specular reflection, can probably be wider than that.

Cycles: wider ray differential calculation for diffuse components of principled BSDF

Cycles: Added ray differential calculation for AO

Cycles: Let OIIO do the sharing of the texture cache, add wider differentials for velvet BSDF

Cycles: Added dNdu to kernel globals on CPU, using it for more accurate ray differentials in specular and glossy reflection

Cycles: ImageTexture node now has dx/dy inputs for offset texture coordinates, being filled out with a hacky shader node duplication a la bump_dx/bump_dy

Cycles: Widened differentials for diffuse and glossy BSDFs for better texture cache performance

Cycles: Fixed texture cache build in Visual Studio - need to tell OIIO to disable AVX

Cycles: removed ?.? at the end of texture cache help text

Cycles: Better quality filtering for .tx mip maps

Cycles: Use texture cache only for CPU devices

Cycles: resetting texture cache stats after use

Cycles: made OSL shading use .tx files where available, added a mutex to the kernel texture name array

Cycles: a handful of fixes for texture caching

Cycles: first additions for OIIO texture caching

* TextureSystem options are exposed in the UI
* Automatic generation of .tx files is optional
* Texture lookups do not use differentials or mip maps yet, so performance is pretty bad