Blender Git Loki

DrawManager: Multithreaded counting of material buckets.

When having multiple materials in a mesh the triangles are sorted based
on material index. This sorting is done single threaded, but needs two
loops over the data. One to count the bucket size and the second one to
add the triangles to the right position in the buckets.

This patch will do the counting in a multithreaded approach that would
speed up the cache creation. It has been measured that this part is the
most blocking part of the cache creation.

Reviewed By: mano-wii

Differential Revision: https://developer.blender.org/D11615