Attempts to substitude CCGDM with an OpenSubdiv based structure
which has less abstraction levels. The missing part in this
substitude is a face pointers which old CCGDM/multires code was
using to stitch faces (averaging boundaries).
Another curial bit missing: "reshaping" of multires CD_MDISPS
to the state of new PBVH grids.
The new code is only available when OpenSubdiv modifier is
enabled (WITH_OPENSUBDIV_MODIFIER=ON) and with debug value of
128. This is so this WIP code is not interfering with current
production machines in the studio.
Reviewers: brecht
Reviewed By: brecht
Differential Revision: https://developer.blender.org/D3685
The function definitions still reside in DerivedMesh.c. Once we're done
porting all the DerivedMesh use to Mesh, we'll move the still-relevant
functions to mesh_runtime.c. This move is now cumbersome due to shared
statically-declared utility functions in DerivedMesh.c
