Blender Git Loki

Sculpt-dev: support area weighted smooth for PBVH_FACES

* This was actually kind of annoying; the
vertex->face-area-list code is in pbvh and
relies on edge ordering
around verts, but that order is non-trivial for
PBVH_FACES (relying as it does on a vertex->poly
map). This ordering was calculated entirely in
editors/sculpt_paint/sculpt.c, not callable from
pbvh.
* The solution was to add a helper function to pbvh
for building vertex->edge lists from vertex->poly
maps. This is then used by both sculpt.c and the
vertex->face-area-list code.

* Also improved boundary bevel smooth a bit. I'm
thinking of extracting it from SCULPT_neighbor_coords_average_interior
into its own function and possibly its own brush.