Blender Git Loki

Fix T51038: `layerInterp_mloopcol` was casting instead of rounding the interpolated RGBA channels

Casting to int truncates a floating-point number, that is, it loose the fractional part.

Cleanup: minor edits to path test

No need for redundant ID's and correct arg order

BLI_path_util: Add BLI_path_join

There weren't any convenient ways to join multiple paths in C
that accounted for corner cases.

Add: BKE_appdir_folder_id_ex

Allows getting the path without using a static string.

Cleanup: line-length

OpenGL: viewport background & depth buffer fixes

Untangling some of the logic in view3d_draw.

bpy.path.display_name: strip spaces

Useful for Python module paths that can't start with numbers.

BLI_path_util: Add string versions of SEP, ALTSEP

This allows for adding separators in string literals.

addon_utils: add disable_all function

OpenGL Immediate Mode: finalize `image_draw`

The directive `#if 0` was ignored.

Part of T49043

Cycles: Remove old non-optimized triangle intersection function

It is unused now and if we want similar function we should use
Pluecker intersection which is same performance with SSE optimization
but which is more watertight.

Cycles: Remove unused macro

Cycles: Use SSE-optimized version of triangle intersection for motion triangles

The title says it all actually. Gives up to 10% speedup on test scenes here
on i7-6800K.

Render times on GPU are unreliable here, but there might be some slowdown
caused by watertight nature of intersections.

Cycles: Fix speed regression on GPU

Avoid construction of temporary array and make utility function force-inlined.
Additionally avoid calling float4_to_float3 twice.

This brings render times to the same values as before current patch series.

Cycles: Use utility function for SSS triangle intersection

This effectively de-duplicates triangle intersection logic implemented
for both regular triangle and SSS triangle.

Cycles: Move watertight triangle intersection to an utility file

This way the code can be reused more easily.

Cycles: Move triangle intersection precalc to an util file

This is a preparation work for the followup commit which wil l move
remaining parts of Woop intersection logic to an utility file.

Doing it as a separate commit to keep changes more atomic and easier
to bisect when/if needed.

Cycles: Cleanup, move utility function to utility file

Was an old TODO, this function is handy for some math utilities as well.

Cycles: Cleanup, code style and comments

Cycles: Move intersection math to own header file

There are following benefits:

- Modifying intersection algorithm will not cause so much re-compilation.
- It works around header dependency hell and allows us to use vectorization
types much easier in there.