Dyntopo: optimize edge collapsing

Checking if faces exist was a bottleneck,
use a simpler version of this function for triangles.

Gives approx 1.6x overall speedup (when many edges are being collapsed).

1 files changed, 43 insertions, 3 deletions

diff --git a/source/blender/blenkernel/intern/pbvh_bmesh.c b/source/blender/blenkernel/intern/pbvh_bmesh.c
index eed3b8a8380..45e33760d15 100644
--- a/source/blender/blenkernel/intern/pbvh_bmesh.c
+++ b/source/blender/blenkernel/intern/pbvh_bmesh.c
@@ -131,6 +131,40 @@ BLI_INLINE void bm_face_as_array_index_tri(BMFace *f, int r_index[3])
 	r_index[2] = BM_elem_index_get(l->v);
 }
 
+/**
+ * A version of #BM_face_exists, optimized for triangles
+ * when we know the loop and the opposite vertex.
+ *
+ * Check if any triangle is formed by (l_radial_first->v, l_radial_first->next->v, v_opposite),
+ * at either winding (since its a triangle no special checks are needed).
+ *
+ * <pre>
+ * l_radial_first->v & l_radial_first->next->v
+ * +---+
+ * |  /
+ * | /
+ * + v_opposite
+ * </pre>
+ *
+ * Its assumed that \a l_radial_first is never forming the target face.
+ */
+static bool bm_face_exists_tri_from_loop_vert(
+        BMLoop *l_radial_first, BMVert *v_opposite, BMFace **r_face_existing)
+{
+	BLI_assert(!ELEM(v_opposite, l_radial_first->v, l_radial_first->next->v, l_radial_first->prev->v));
+	if (l_radial_first->radial_next != l_radial_first) {
+		BMLoop *l_radial_iter = l_radial_first->radial_next;
+		do {
+			BLI_assert(l_radial_iter->f->len == 3);
+			if (l_radial_iter->prev->v == v_opposite) {
+				*r_face_existing = l_radial_iter->f;
+				return true;
+			}
+		} while ((l_radial_iter = l_radial_iter->radial_next) != l_radial_first);
+	}
+	return false;
+}
+
 /** \} */
 
 
@@ -1244,19 +1278,25 @@ static void pbvh_bmesh_collapse_edge(
 				v_tri[i] = v_conn;
 			}
 		}
-#else
-		BMVert *v_tri[3] = {v_conn, l->next->v, l->prev->v};
 #endif
 
 		/* Check if a face using these vertices already exists. If so,
 		 * skip adding this face and mark the existing one for
 		 * deletion as well. Prevents extraneous "flaps" from being
 		 * created. */
-		if (BM_face_exists(v_tri, 3, &existing_face)) {
+#if 0
+		if (UNLIKELY(BM_face_exists(v_tri, 3, &existing_face)))
+#else
+		if (UNLIKELY(bm_face_exists_tri_from_loop_vert(l->next, v_conn, &existing_face)))
+#endif
+		{
 			BLI_assert(existing_face);
 			BLI_buffer_append(deleted_faces, BMFace *, existing_face);
 		}
 		else {
+			BMVert *v_tri[3] = {v_conn, l->next->v, l->prev->v};
+
+			BLI_assert(BM_face_exists(v_tri, 3, NULL) == false);
 			BMEdge *e_tri[3];
 			PBVHNode *n = pbvh_bmesh_node_from_face(bvh, f);
 			int ni = n - bvh->nodes;