un-subdivide bmesh operator, useful for making lower polygon versions of models, can give nicer results then edge collapsing which tends to give a lot of sharp triangles.

works on edges and faces, has iteration option to further reduce the poly count.

access from the edge menu, under subdivide.

example: http://www.graphicall.org/ftp/ideasman42/bmesh_unsubdivide.png

4 files changed, 58 insertions, 3 deletions

diff --git a/source/blender/editors/mesh/editmesh_select.c b/source/blender/editors/mesh/editmesh_select.c
index fe3860de839..40132c697e6 100644
--- a/source/blender/editors/mesh/editmesh_select.c
+++ b/source/blender/editors/mesh/editmesh_select.c
@@ -2165,11 +2165,19 @@ static void walker_deselect_nth(BMEditMesh *em, int nth, int offset, BMHeader *h
 	         BMW_FLAG_NOP, /* don't use BMW_FLAG_TEST_HIDDEN here since we want to desel all */
 	         BMW_NIL_LAY);
 
+	/* use tag to avoid touching the same verts twice */
+	BM_ITER_MESH (ele, &iter, bm, itertype) {
+		BM_elem_flag_disable(ele, BM_ELEM_TAG);
+	}
+
 	BLI_assert(walker.order == BMW_BREADTH_FIRST);
 	for (ele = BMW_begin(&walker, h_act); ele != NULL; ele = BMW_step(&walker)) {
-		/* Deselect elements that aren't at "nth" depth from active */
-		if ((offset + BMW_current_depth(&walker)) % nth) {
-			BM_elem_select_set(bm, ele, FALSE);
+		if (!BM_elem_flag_test(ele, BM_ELEM_TAG)) {
+			/* Deselect elements that aren't at "nth" depth from active */
+			if ((offset + BMW_current_depth(&walker)) % nth) {
+				BM_elem_select_set(bm, ele, FALSE);
+			}
+			BM_elem_flag_enable(ele, BM_ELEM_TAG);
 		}
 	}
 	BMW_end(&walker);
diff --git a/source/blender/editors/mesh/editmesh_tools.c b/source/blender/editors/mesh/editmesh_tools.c
index 1507597feeb..3255853442a 100644
--- a/source/blender/editors/mesh/editmesh_tools.c
+++ b/source/blender/editors/mesh/editmesh_tools.c
@@ -156,6 +156,51 @@ void MESH_OT_subdivide(wmOperatorType *ot)
 }
 
 
+static int edbm_unsubdivide_exec(bContext *C, wmOperator *op)
+{
+	Object *obedit = CTX_data_edit_object(C);
+	BMEditMesh *em = BMEdit_FromObject(obedit);
+	BMOperator bmop;
+
+	int iterations = RNA_int_get(op->ptr, "iterations");
+
+	EDBM_op_init(em, &bmop, op,
+	             "unsubdivide verts=%hv iterations=%i", BM_ELEM_SELECT, iterations);
+
+	BMO_op_exec(em->bm, &bmop);
+
+	if (!EDBM_op_finish(em, &bmop, op, TRUE)) {
+		return 0;
+	}
+
+	if ((em->selectmode & SCE_SELECT_VERTEX) == 0) {
+		EDBM_selectmode_flush_ex(em, SCE_SELECT_VERTEX);  /* need to flush vert->face first */
+	}
+	EDBM_selectmode_flush(em);
+
+	EDBM_update_generic(C, em, TRUE);
+
+	return OPERATOR_FINISHED;
+}
+
+void MESH_OT_unsubdivide(wmOperatorType *ot)
+{
+	/* identifiers */
+	ot->name = "Un-Subdivide";
+	ot->description = "UnSubdivide selected edges & faces";
+	ot->idname = "MESH_OT_unsubdivide";
+
+	/* api callbacks */
+	ot->exec = edbm_unsubdivide_exec;
+	ot->poll = ED_operator_editmesh;
+
+	/* flags */
+	ot->flag = OPTYPE_REGISTER | OPTYPE_UNDO;
+
+	/* props */
+	RNA_def_int(ot->srna, "iterations", 2, 1, INT_MAX, "Iterations", "Number of times to unsubdivide", 1, 100);
+}
+
 void EMBM_project_snap_verts(bContext *C, ARegion *ar, BMEditMesh *em)
 {
 	Object *obedit = em->ob;
diff --git a/source/blender/editors/mesh/mesh_intern.h b/source/blender/editors/mesh/mesh_intern.h
index 5fcf4fe4377..5c782dc2266 100644
--- a/source/blender/editors/mesh/mesh_intern.h
+++ b/source/blender/editors/mesh/mesh_intern.h
@@ -144,6 +144,7 @@ extern struct EnumPropertyItem *corner_type_items;
 
 void MESH_OT_merge(struct wmOperatorType *ot);
 void MESH_OT_subdivide(struct wmOperatorType *ot);
+void MESH_OT_unsubdivide(struct wmOperatorType *ot);
 void MESH_OT_remove_doubles(struct wmOperatorType *ot);
 void MESH_OT_spin(struct wmOperatorType *ot);
 void MESH_OT_screw(struct wmOperatorType *ot);
diff --git a/source/blender/editors/mesh/mesh_ops.c b/source/blender/editors/mesh/mesh_ops.c
index 8a575e57a60..c4e8fd70989 100644
--- a/source/blender/editors/mesh/mesh_ops.c
+++ b/source/blender/editors/mesh/mesh_ops.c
@@ -74,6 +74,7 @@ void ED_operatortypes_mesh(void)
 	WM_operatortype_append(MESH_OT_normals_make_consistent);
 	WM_operatortype_append(MESH_OT_merge);
 	WM_operatortype_append(MESH_OT_subdivide);
+	WM_operatortype_append(MESH_OT_unsubdivide);
 	WM_operatortype_append(MESH_OT_faces_select_linked_flat);
 	WM_operatortype_append(MESH_OT_edges_select_sharp);
 	WM_operatortype_append(MESH_OT_primitive_plane_add);