fix [#32500] Odd behaviour with subdividing an ngon

diff --git a/source/blender/bmesh/operators/bmo_subdivide.c b/source/blender/bmesh/operators/bmo_subdivide.c
index 5fb7c8254a11ec79c3dec56024331efff9856293..ade560edd49f158723c4d91cb15844e409472563 100644 (file)
--- a/source/blender/bmesh/operators/bmo_subdivide.c
+++ b/source/blender/bmesh/operators/bmo_subdivide.c
@@ -977,8 +977,44 @@ void bmo_subdivide_edges_exec(BMesh *bm, BMOperator *op)
 
                        BLI_array_grow_items(loops_split, numcuts);
                        for (j = 0; j < numcuts; j++) {
-                               loops_split[j][0] = loops[a];
-                               loops_split[j][1] = loops[b];
+                               int ok = TRUE;
+
+                               /* Check for special case: [#32500]
+                                * This edge pair could be used by more then one face,
+                                * in this case it used to (2.63), split both faces along the same verts
+                                * while it could be calculated which face should do the split,
+                                * its ambigious, so in this case we're better off to skip them as exceptional cases
+                                * and not try to be clever guessing which face to cut up.
+                                *
+                                * To avoid this case we need to check:
+                                * Do the verts of each loop share a face (but not connect to make an edge of that face)
+                                */
+                               {
+                                       BMLoop *other_loop;
+                                       BMIter other_fiter;
+                                       BM_ITER_ELEM (other_loop, &other_fiter, loops[a]->v, BM_LOOPS_OF_VERT) {
+                                               if (other_loop->f != face) {
+                                                       if (BM_vert_in_face(other_loop->f, loops[a]->v)) {
+                                                               /* we assume that these verts are not making an edge in the face */
+                                                               BLI_assert(other_loop->prev->v != loops[a]->v);
+                                                               BLI_assert(other_loop->next->v != loops[a]->v);
+
+                                                               ok = FALSE;
+                                                               break;
+                                                       }
+                                               }
+                                       }
+                               }
+
+
+                               if (ok == TRUE) {
+                                       loops_split[j][0] = loops[a];
+                                       loops_split[j][1] = loops[b];
+                               }
+                               else {
+                                       loops_split[j][0] = NULL;
+                                       loops_split[j][1] = NULL;
+                               }
 
                                b = (b - 1) % vlen;
                                a = (a + 1) % vlen;
@@ -993,6 +1029,8 @@ void bmo_subdivide_edges_exec(BMesh *bm, BMOperator *op)
 
                        for (j = 0; j < BLI_array_count(loops_split); j++) {
                                if (loops_split[j][0]) {
+                                       BLI_assert(BM_edge_exists(loops_split[j][0]->v, loops_split[j][1]->v) == FALSE);
+
                                        /* BMFace *nf = */ /* UNUSED */
                                        BM_face_split(bm, face, loops_split[j][0]->v, loops_split[j][1]->v, &nl, NULL, FALSE);
                                }