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 idea is to create vertices along the coarse edges once, without
splitting coarse edges on separate ptex faces. This requires some
indexing magic, vertices within a patch are no longer sequential.
Not sure how to make it nicer without such a black magic looking
calculations (which are basically boiling down to mimicking order
of verts/edges creation).
In the current offsets calculation loose verts and edges are not
properly taken into account, but those are causing topology refiner
to fail anyway, so it needs a bit deeper change.
Reviewers: brecht
Differential Revision: https://developer.blender.org/D3570
