Blender Git Loki

Review update: fix exporter UI.

Cleanup: GPUFrameBuffer: Use Texture class instead of gl calls

Change bsdf values as per illum values.

Set defaults of MTLMaterial that is useful for importer.
For exporter, asserts have been added.

Export loop normals not vertex normals.

Don't write default scale and translation.

Also fix debug warning of material not found.

Add asserts to catch unchanged values.

Add float3 to string function to utilities.

Makes the MTL writer a bit compact. That change to be committed soon.

Move string utility functions in one file.

No functional change. Only renaming, and adding a few const.

GLTexture: Add back texture proxy check

Cleanup the feature itself:
- Check 3D textures size against the correct limit.
- Add check for compressed textures.

GPUTexture: Add support for samplers

This just add back the support.
This commit also includes a bit of cleanup.

GPUTexture: GL Backend Isolation

This is a massive cleanup needed for vulkan support T68990. It provides:

- More meaningful enums with conversion functions.
- Less hacky supports of arrays and cubemaps (all considered layered).
- More inline with the stateless design of vulkan and modern GL.
- Methods Fallbacks are using framebuffer functions that are wrapped
instead of implementing inside the texture module.

What is not in there:
- API change.
- Samplers support (breaks a few effects).

GPUFramebuffer: Encapsulate single attachement clear

This is in preparation of using it to clear single texture.

Also includes minor cleanups about not using tex target in
assert and adding enum operators.

Cleanup: EEVEE: Use correct array size and use equals_v2v2_int

GPUTexture: Add skeleton of the new GLTexture class

GPUTexture: Remove bind to edit calls

This is going to be unecessary after the GPU opengl texture backend refactor.

For now add a save/restore mechanism to leave the state untouched.

Also remove some calls where the caller would bind to particular binding
point and set the shader uniform.

Custom Menus : merge master

Merge branch 'greasepencil-edit-curve' into soc-2020-greasepencil-curve

Merge branch 'master' into greasepencil-edit-curve

Merge branch 'master' into greasepencil-object

Rename vert_treplet to vert_index_mlen; add comments

Minor fixes, use scoped_timer for export too.