Multires: Initial work to get sculpting to work with OpenSubdiv

Allows to go to sculpt mode, do brush strokes, get out of sculpt mode
and have deformation preserved.

The issues currently is that the current implementation of CCG
storage is created from the limit surface, without displacement
taken into account. It is trivial to get displaced coordinates,
but it is more tricky to get displaced normals. This is something
to be solved next.

Another limitation is that this only works for sculpting at a maximal
multires level. There is code to be done to support propagation
of displacement onto a higher levels.

1 files changed, 4 insertions, 0 deletions

diff --git a/source/blender/blenkernel/BKE_paint.h b/source/blender/blenkernel/BKE_paint.h
index ade23a2a9ca..d2d09609221 100644
--- a/source/blender/blenkernel/BKE_paint.h
+++ b/source/blender/blenkernel/BKE_paint.h
@@ -56,6 +56,7 @@ struct Scene;
 struct ViewLayer;
 struct Sculpt;
 struct StrokeCache;
+struct SubdivCCG;
 struct Tex;
 struct ImagePool;
 struct UnifiedPaintSettings;
@@ -198,6 +199,9 @@ typedef struct SculptSession {
 	/* Undo/redo log for dynamic topology sculpting */
 	struct BMLog *bm_log;
 
+	/* Limit surface/grids. */
+	struct SubdivCCG *subdiv_ccg;
+
 	/* PBVH acceleration structure */
 	struct PBVH *pbvh;
 	bool show_diffuse_color;