[Bf-blender-cvs] [bd76184966a] master: Fix sculpt neighbor iterator not taking visibility into account

[Pablo Dobarro]

Commit: bd76184966add88911c03986a59a42911e8663fa
Author: Pablo Dobarro
Date:   Fri May 14 03:07:18 2021 +0200
Branches: master
https://developer.blender.org/rBbd76184966add88911c03986a59a42911e8663fa

Fix sculpt neighbor iterator not taking visibility into account

Sculpting tools are designed to ignore hidden geometry and behave like
hidden geometry does not exist.
When getting the neighbors of a vertex, now this takes into account
hidden geometry to avoid returing neighbors which connected edge is not
visible. This should make corner cases of a lot of tools work properly,
especially when working in low poly meshes when is common to have a
single face loop hidden.

Reviewed By: JacquesLucke

Differential Revision: https://developer.blender.org/D11007

===================================================================

M	source/blender/blenkernel/BKE_paint.h
M	source/blender/editors/sculpt_paint/sculpt.c

===================================================================

diff --git a/source/blender/blenkernel/BKE_paint.h b/source/blender/blenkernel/BKE_paint.h
index 228b52123f3..73413b61456 100644
--- a/source/blender/blenkernel/BKE_paint.h
+++ b/source/blender/blenkernel/BKE_paint.h
@@ -486,7 +486,11 @@ typedef struct SculptSession {
   /* Total number of polys of the base mesh. */
   int totfaces;
   /* Face sets store its visibility in the sign of the integer, using the absolute value as the
-   * Face Set ID. Positive IDs are visible, negative IDs are hidden. */
+   * Face Set ID. Positive IDs are visible, negative IDs are hidden.
+   * The 0 ID is not used by the tools or the visibility system, it is just used when creating new
+   * geometry (the trim tool, for example) to detect which geometry was just added, so it can be
+   * assigned a valid Face Set after creation. Tools are not intended to run with Face Sets IDs set
+   * to 0. */
   int *face_sets;
 
   /* BMesh for dynamic topology sculpting */
diff --git a/source/blender/editors/sculpt_paint/sculpt.c b/source/blender/editors/sculpt_paint/sculpt.c
index 7817257a98d..2e1dd928f96 100644
--- a/source/blender/editors/sculpt_paint/sculpt.c
+++ b/source/blender/editors/sculpt_paint/sculpt.c
@@ -780,6 +780,10 @@ static void sculpt_vertex_neighbors_get_faces(SculptSession *ss,
   iter->neighbors = iter->neighbors_fixed;
 
   for (int i = 0; i < ss->pmap[index].count; i++) {
+    if (ss->face_sets[vert_map->indices[i]] < 0) {
+      /* Skip connectivity from hidden faces. */
+      continue;
+    }
     const MPoly *p = &ss->mpoly[vert_map->indices[i]];
     uint f_adj_v[2];
     if (poly_get_adj_loops_from_vert(p, ss->mloop, index, f_adj_v) != -1) {