BMesh: new API call to collapse an edge

Existing collapse functions were strict regarding the number of verts sharing an edge.
BM_edge_collapse allows any edge to be passed in without first having to manipulate geometry.

source/blender/bmesh/intern/bmesh_core.c

@@ -1855,6 +1855,104 @@ BMEdge *bmesh_jekv(
 	return NULL;
 }
 
+/**
+ * \brief Join Vert Kill Edge (JVKE)
+ *
+ * Collapse an edge, merging surrounding data.
+ *
+ * Unlike #BM_vert_collapse_edge & #bmesh_jekv which only handle 2 valence verts,
+ * this can handle any number of connected edges/faces.
+ *
+ * <pre>
+ * Before: -> After:
+ * +-+-+-+    +-+-+-+
+ * | | | |    | \ / |
+ * +-+-+-+    +--+--+
+ * | | | |    | / \ |
+ * +-+-+-+    +-+-+-+
+ * </pre>
+ */
+BMVert *bmesh_jvke(
+        BMesh *bm, BMEdge *e_kill, BMVert *v_kill,
+        const bool do_del, const bool check_edge_double,
+        const bool kill_degenerate_faces)
+{
+	BLI_SMALLSTACK_DECLARE(faces_degenerate, BMFace *);
+	BMVert *v_target = BM_edge_other_vert(e_kill, v_kill);
+
+	BLI_assert(BM_vert_in_edge(e_kill, v_kill));
+
+	if (e_kill->l) {
+		BMLoop *l_kill, *l_first, *l_kill_next;
+		l_kill = l_first = e_kill->l;
+		do {
+			/* relink loops and fix vertex pointer */
+			if (l_kill->next->v == v_kill) {
+				l_kill->next->v = v_target;
+			}
+
+			l_kill->next->prev = l_kill->prev;
+			l_kill->prev->next = l_kill->next;
+			if (BM_FACE_FIRST_LOOP(l_kill->f) == l_kill) {
+				BM_FACE_FIRST_LOOP(l_kill->f) = l_kill->next;
+			}
+
+			/* fix len attribute of face */
+			l_kill->f->len--;
+			if (kill_degenerate_faces) {
+				if (l_kill->f->len < 3) {
+					BLI_SMALLSTACK_PUSH(faces_degenerate, l_kill->f);
+				}
+			}
+			l_kill_next = l_kill->radial_next;
+
+			bm_kill_only_loop(bm, l_kill);
+
+		} while ((l_kill = l_kill_next) != l_first);
+
+		e_kill->l = NULL;
+	}
+
+	BM_edge_kill(bm, e_kill);
+	BM_CHECK_ELEMENT(v_kill);
+	BM_CHECK_ELEMENT(v_target);
+
+	if (v_target->e && v_kill->e) {
+		/* inline BM_vert_splice(bm, v_target, v_kill); */
+		BMEdge *e;
+		while ((e = v_kill->e)) {
+			BMEdge *e_target;
+
+			if (check_edge_double) {
+				e_target = BM_edge_exists(v_target, BM_edge_other_vert(e, v_kill));
+			}
+
+			bmesh_edge_vert_swap(e, v_target, v_kill);
+			BLI_assert(e->v1 != e->v2);
+
+			if (check_edge_double) {
+				if (e_target) {
+					BM_edge_splice(bm, e_target, e);
+				}
+			}
+		}
+	}
+
+	if (kill_degenerate_faces) {
+		BMFace *f_kill;
+		while ((f_kill = BLI_SMALLSTACK_POP(faces_degenerate))) {
+			BM_face_kill(bm, f_kill);
+		}
+	}
+
+	if (do_del) {
+		BLI_assert(v_kill->e == NULL);
+		bm_kill_only_vert(bm, v_kill);
+	}
+
+	return v_target;
+}
+
 /**
  * \brief Join Face Kill Edge (JFKE)
  *

source/blender/bmesh/intern/bmesh_core.h

@@ -100,6 +100,10 @@ BMEdge *bmesh_jekv(
         BMesh *bm, BMEdge *e_kill, BMVert *v_kill,
         const bool do_del, const bool check_edge_splice,
         const bool kill_degenerate_faces);
+BMVert *bmesh_jvke(
+        BMesh *bm, BMEdge *e_kill, BMVert *v_kill,
+        const bool do_del, const bool check_edge_double,
+        const bool kill_degenerate_faces);
 BMFace *bmesh_jfke(BMesh *bm, BMFace *f1, BMFace *f2, BMEdge *e);
 BMVert *bmesh_urmv(BMesh *bm, BMFace *f_sep, BMVert *v_sep);
 BMVert *bmesh_urmv_loop(BMesh *bm, BMLoop *l_sep);

source/blender/bmesh/intern/bmesh_mods.c

@@ -1116,6 +1116,16 @@ BMEdge *BM_vert_collapse_edge(
 
 #undef DO_V_INTERP
 
+/**
+ * Collapse and edge into a single vertex.
+ */
+BMVert *BM_edge_collapse(
+        BMesh *bm, BMEdge *e_kill, BMVert *v_kill,
+        const bool do_del, const bool kill_degenerate_faces)
+{
+	return bmesh_jvke(bm, e_kill, v_kill, do_del, true, kill_degenerate_faces);
+}
+
 /**
  * \brief Edge Split
  *

source/blender/bmesh/intern/bmesh_mods.h

@@ -59,6 +59,9 @@ BMEdge *BM_vert_collapse_edge(
         BMesh *bm, BMEdge *e_kill, BMVert *v_kill,
         const bool do_del, const bool kill_degenerate_faces);
 
+BMVert *BM_edge_collapse(
+        BMesh *bm, BMEdge *e_kill, BMVert *v_kill,
+        const bool do_del, const bool kill_degenerate_faces);
 
 BMVert *BM_edge_split(BMesh *bm, BMEdge *e, BMVert *v, BMEdge **r_e, float percent);