Initial implementation of mdisps layer interpolation

Sculpt data shouldn't be lost when making topology changes without
quads<->tris face converison.

General idea:
- Go through all grid points of each corner and convert per-corner
  coordiante to per-face cooredinate
- Apply weights and convert new point to per-corner coordinate
- Use bilinear interpolation to get needed displacement vector

Some additional work was necessery:
- Two neighbour corners could have different displacements along common
  boundary. multires_mdisp_smooth_bounds() makes displacement "symmetrical"
- Point could change it's corner, so displacement vector should be flipped
  in some way. In some cases it's not only flipping, because corner could
  be mapped with some rotation. It's not solved for triangular faces yet,
  so only z-axis displacement would be interpolated for tris.

More limitations:
- Interpolation will give incorrect result after quad<->triangle
  face conversion.
- When face normal was fillped displacement would change it's direction too.

1 files changed, 1 insertions, 0 deletions

diff --git a/source/blender/blenkernel/BKE_multires.h b/source/blender/blenkernel/BKE_multires.h
index 6520ef0df63..8fb80292ffb 100644
--- a/source/blender/blenkernel/BKE_multires.h
+++ b/source/blender/blenkernel/BKE_multires.h
@@ -76,6 +76,7 @@ void multiresModifier_scale_disp(struct Scene *scene, struct Object *ob);
 void multiresModifier_prepare_join(struct Scene *scene, struct Object *ob, struct Object *to_ob);
 
 int multires_mdisp_corners(struct MDisps *s);
+void multires_mdisp_smooth_bounds(struct MDisps *disps);
 
 /* update multires data after topology changing */
 void multires_topology_changed(struct Object *ob);