add BM_edge_find_double() and use in bmesh decimator to fix crash.

3 files changed, 49 insertions, 1 deletions

diff --git a/source/blender/bmesh/intern/bmesh_decimate.c b/source/blender/bmesh/intern/bmesh_decimate.c
index 122f24955c6..519bdba02a9 100644
--- a/source/blender/bmesh/intern/bmesh_decimate.c
+++ b/source/blender/bmesh/intern/bmesh_decimate.c
@@ -503,8 +503,31 @@ static void bm_decim_edge_collapse(BMesh *bm, BMEdge *e,
 			BMEdge *e_first;
 			e_iter = e_first = v->e;
 			do {
+				//BLI_assert(BM_edge_find_double(e_iter) == NULL);
+#ifdef USE_SAFETY_CHECKS
+				/* note! - this check is slow, but we can't avoid it - Campbell */
+				BMEdge *e_double;
+
+				e_double = BM_edge_find_double(e_iter);
+
+				if (UNLIKELY(e_double != NULL)) {
+					int e_index = BM_elem_index_get(e_double);
+					if (BM_edge_splice(bm, e_double, e_iter)) {
+						if (eheap_table[e_index]) {
+							BLI_heap_remove(eheap, eheap_table[e_index]);
+							eheap_table[e_index] = NULL;
+						}
+					}
+				}
+
+				/* if this happens, the e_double check could be put in a while loop,
+				 * so as to keep removing doubles while they are found. so far this isnt needed */
+				BLI_assert(BM_edge_find_double(e_iter) == NULL);
+#endif
+
 				bm_decim_build_edge_cost_single(e_iter, vquadrics, eheap, eheap_table);
 			} while ((e_iter = bmesh_disk_edge_next(e_iter, v)) != e_first);
+
 		}
 	}
 }
@@ -566,9 +589,11 @@ void BM_mesh_decimate(BMesh *bm, const float factor)
 	}
 #endif
 
-
 	/* free vars */
 	MEM_freeN(vquadrics);
 	MEM_freeN(eheap_table);
 	BLI_heap_free(eheap, NULL);
+
+	/* testing only */
+	// BM_mesh_validate(bm);
 }
diff --git a/source/blender/bmesh/intern/bmesh_queries.c b/source/blender/bmesh/intern/bmesh_queries.c
index 6bf4e3db1d3..9520b0298d8 100644
--- a/source/blender/bmesh/intern/bmesh_queries.c
+++ b/source/blender/bmesh/intern/bmesh_queries.c
@@ -1064,6 +1064,28 @@ BMEdge *BM_edge_exists(BMVert *v1, BMVert *v2)
 }
 
 /**
+ * Returns an edge sharing the same vertices as this one.
+ * This isn't an invalid state but tools should clean up these cases before
+ * returning the mesh to the user.
+ */
+BMEdge *BM_edge_find_double(BMEdge *e)
+{
+	BMVert *v       = e->v1;
+	BMVert *v_other = e->v2;
+
+	BMEdge *e_iter;
+
+	e_iter = e;
+	while ((e_iter = bmesh_disk_edge_next(e_iter, v)) != e) {
+		if (UNLIKELY(BM_vert_in_edge(e_iter, v_other))) {
+			return e_iter;
+		}
+	}
+
+	return NULL;
+}
+
+/**
  * Given a set of vertices \a varr, find out if
  * all those vertices overlap an existing face.
  *
diff --git a/source/blender/bmesh/intern/bmesh_queries.h b/source/blender/bmesh/intern/bmesh_queries.h
index 84a5ffacec7..166b8a54f8a 100644
--- a/source/blender/bmesh/intern/bmesh_queries.h
+++ b/source/blender/bmesh/intern/bmesh_queries.h
@@ -74,6 +74,7 @@ BMLoop *BM_face_find_shortest_loop(BMFace *f);
 BMLoop *BM_face_find_longest_loop(BMFace *f);
 
 BMEdge *BM_edge_exists(BMVert *v1, BMVert *v2);
+BMEdge *BM_edge_find_double(BMEdge *e);
 
 int     BM_face_exists_overlap(BMesh *bm, BMVert **varr, int len, BMFace **r_existface);