Add BMesh and WM symmetrize operators

* The symmetrize operation makes the input mesh elements symmetrical,
  but unlike mirroring it only copies in one direction. The edges and
  faces that cross the plane of symmetry are split as needed to
  enforce symmetry.

* The symmetrize operator can be controlled with the "direction"
  property, which combines the choices of symmetry plane and
  positive-negative/negative-positive. The enum for this is
  BMO_SymmDirection.

* Added menu items in the top-level Mesh menu and the WKEY specials
  menu.

* Documentation:
  http://wiki.blender.org/index.php/User:Nicholasbishop/Symmetrize

* Reviewed by Brecht:
  https://codereview.appspot.com/6618059

3 files changed, 57 insertions, 0 deletions

diff --git a/source/blender/editors/mesh/editmesh_tools.c b/source/blender/editors/mesh/editmesh_tools.c
index 69cfe79728e..d8dce98a009 100644
--- a/source/blender/editors/mesh/editmesh_tools.c
+++ b/source/blender/editors/mesh/editmesh_tools.c
@@ -41,6 +41,7 @@
 #include "RNA_define.h"
 #include "RNA_access.h"
 
+#include "BLI_array.h"
 #include "BLI_blenlib.h"
 #include "BLI_noise.h"
 #include "BLI_math.h"
@@ -50,6 +51,7 @@
 #include "BKE_context.h"
 #include "BKE_cdderivedmesh.h"
 #include "BKE_depsgraph.h"
+#include "BKE_mesh.h"
 #include "BKE_object.h"
 #include "BKE_report.h"
 #include "BKE_texture.h"
@@ -5393,3 +5395,54 @@ void MESH_OT_convex_hull(wmOperatorType *ot)
 
 	join_triangle_props(ot);
 }
+
+static int mesh_symmetrize_exec(bContext *C, wmOperator *op)
+{
+	Object *obedit = CTX_data_edit_object(C);
+	BMEditMesh *em = BMEdit_FromObject(obedit);
+	BMOperator bmop;
+
+	EDBM_op_init(em, &bmop, op, "symmetrize input=%hvef direction=%i",
+				 BM_ELEM_SELECT, RNA_enum_get(op->ptr, "direction"));
+	BMO_op_exec(em->bm, &bmop);
+
+	if (!EDBM_op_finish(em, &bmop, op, TRUE)) {
+		return OPERATOR_CANCELLED;
+	}
+	else {
+		EDBM_update_generic(C, em, TRUE);
+		EDBM_selectmode_flush(em);
+		return OPERATOR_FINISHED;
+	}
+}
+
+void MESH_OT_symmetrize(struct wmOperatorType *ot)
+{
+	static EnumPropertyItem direction_items[] = {
+		{BMO_SYMMETRIZE_NEGATIVE_X, "NEGATIVE_X", 0, "-X to +X", ""},
+		{BMO_SYMMETRIZE_POSITIVE_X, "POSITIVE_X", 0, "+X to -X", ""},
+
+		{BMO_SYMMETRIZE_NEGATIVE_Y, "NEGATIVE_Y", 0, "-Y to +Y", ""},
+		{BMO_SYMMETRIZE_POSITIVE_Y, "POSITIVE_Y", 0, "+Y to -Y", ""},
+
+		{BMO_SYMMETRIZE_NEGATIVE_Z, "NEGATIVE_Z", 0, "-Z to +Z", ""},
+		{BMO_SYMMETRIZE_POSITIVE_Z, "POSITIVE_Z", 0, "+Z to -Z", ""},
+		{0, NULL, 0, NULL, NULL},
+	};
+
+	/* identifiers */
+	ot->name = "Symmetrize";
+	ot->description = "Enforce symmetry (both form and topological) across an axis";
+	ot->idname = "MESH_OT_symmetrize";
+
+	/* api callbacks */
+	ot->exec = mesh_symmetrize_exec;
+	ot->poll = ED_operator_editmesh;
+
+	/* flags */
+	ot->flag = OPTYPE_REGISTER | OPTYPE_UNDO;
+
+	ot->prop = RNA_def_enum(ot->srna, "direction", direction_items,
+							BMO_SYMMETRIZE_NEGATIVE_X,
+							"Direction", "Which sides to copy from and to");
+}
diff --git a/source/blender/editors/mesh/mesh_intern.h b/source/blender/editors/mesh/mesh_intern.h
index 2676316c66d..5fcf4fe4377 100644
--- a/source/blender/editors/mesh/mesh_intern.h
+++ b/source/blender/editors/mesh/mesh_intern.h
@@ -214,6 +214,8 @@ void MESH_OT_vert_slide(struct wmOperatorType *ot);
 
 void MESH_OT_convex_hull(struct wmOperatorType *ot);
 
+void MESH_OT_symmetrize(struct wmOperatorType *ot);
+
 /* ******************* mesh_navmesh.c */
 void MESH_OT_navmesh_make(struct wmOperatorType *ot);
 void MESH_OT_navmesh_face_copy(struct wmOperatorType *ot);
diff --git a/source/blender/editors/mesh/mesh_ops.c b/source/blender/editors/mesh/mesh_ops.c
index 8ba9b3fe4e7..8a575e57a60 100644
--- a/source/blender/editors/mesh/mesh_ops.c
+++ b/source/blender/editors/mesh/mesh_ops.c
@@ -166,6 +166,8 @@ void ED_operatortypes_mesh(void)
 
 	WM_operatortype_append(MESH_OT_convex_hull);
 
+	WM_operatortype_append(MESH_OT_symmetrize);
+
 #ifdef WITH_GAMEENGINE
 	WM_operatortype_append(MESH_OT_navmesh_make);
 	WM_operatortype_append(MESH_OT_navmesh_face_copy);