Armature Symmetrize tool

D1147 by @julien, with fixes/improvements

Duplicate bones where needed, otherwise use existing.
Keeps parent relations intact, can operate on parts of an armature.

release/scripts/startup/bl_ui/space_view3d.py

@@ -2710,6 +2710,7 @@ class VIEW3D_MT_edit_armature(Menu):
         layout.separator()
 
         layout.operator_context = 'EXEC_AREA'
+        layout.operator("armature.symmetrize")
         layout.operator("armature.autoside_names", text="AutoName Left/Right").type = 'XAXIS'
         layout.operator("armature.autoside_names", text="AutoName Front/Back").type = 'YAXIS'
         layout.operator("armature.autoside_names", text="AutoName Top/Bottom").type = 'ZAXIS'
@@ -2748,6 +2749,7 @@ class VIEW3D_MT_armature_specials(Menu):
         layout.operator("armature.autoside_names", text="AutoName Front/Back").type = 'YAXIS'
         layout.operator("armature.autoside_names", text="AutoName Top/Bottom").type = 'ZAXIS'
         layout.operator("armature.flip_names", text="Flip Names")
+        layout.operator("armature.symmetrize")
 
 
 class VIEW3D_MT_edit_armature_parent(Menu):

source/blender/editors/armature/armature_add.c

@@ -43,6 +43,7 @@
 #include "BKE_constraint.h"
 #include "BKE_context.h"
 #include "BKE_idprop.h"
+#include "BKE_deform.h"
 
 #include "RNA_access.h"
 #include "RNA_define.h"
@@ -516,6 +517,212 @@ void ARMATURE_OT_duplicate(wmOperatorType *ot)
 	ot->flag = OPTYPE_REGISTER | OPTYPE_UNDO;
 }
 
+/**
+ * near duplicate of #armature_duplicate_selected_exec,
+ * except for parenting part (keep in sync)
+ */
+static int armature_symmetrize_exec(bContext *C, wmOperator *op)
+{
+	bArmature *arm;
+	EditBone *ebone_iter;
+	EditBone *ebone_first_dupe = NULL;  /* The beginning of the duplicated mirrored bones in the edbo list */
+
+	Object *obedit = CTX_data_edit_object(C);
+	const int direction = RNA_enum_get(op->ptr, "direction");
+	const int axis = 0;
+
+	arm = obedit->data;
+
+	/* cancel if nothing selected */
+	if (CTX_DATA_COUNT(C, selected_bones) == 0)
+		return OPERATOR_CANCELLED;
+
+	ED_armature_sync_selection(arm->edbo); // XXX why is this needed?
+
+	preEditBoneDuplicate(arm->edbo);
+
+	/* Select mirrored bones */
+	for (ebone_iter = arm->edbo->first; ebone_iter; ebone_iter = ebone_iter->next) {
+		if (EBONE_VISIBLE(arm, ebone_iter) &&
+		    (ebone_iter->flag & BONE_SELECTED))
+		{
+			char name_flip[MAX_VGROUP_NAME];
+
+			BKE_deform_flip_side_name(name_flip, ebone_iter->name, false);
+
+			if (STREQ(name_flip, ebone_iter->name)) {
+				/* if the name matches, we don't have the potential to be mirrored, just skip */
+				ebone_iter->flag &= ~(BONE_SELECTED | BONE_TIPSEL | BONE_ROOTSEL);
+			}
+			else {
+				EditBone *ebone = ED_armature_bone_find_name(arm->edbo, name_flip);
+
+				if (ebone) {
+					if ((ebone->flag & BONE_SELECTED) == 0) {
+						/* simple case, we're selected, the other bone isn't! */
+						ebone_iter->temp = ebone;
+					}
+					else {
+						/* complicated - choose which direction to copy */
+						float axis_delta;
+
+						axis_delta = ebone->head[axis] - ebone_iter->head[axis];
+						if (axis_delta == 0.0f) {
+							axis_delta = ebone->tail[axis] - ebone_iter->tail[axis];
+						}
+
+						if (axis_delta == 0.0f) {
+							/* both mirrored bones exist and point to eachother and overlap exactly.
+							 *
+							 * in this case theres no well defined solution, so de-select both and skip.
+							 */
+							ebone->flag      &= ~(BONE_SELECTED | BONE_TIPSEL | BONE_ROOTSEL);
+							ebone_iter->flag &= ~(BONE_SELECTED | BONE_TIPSEL | BONE_ROOTSEL);
+						}
+						else {
+							EditBone *ebone_src, *ebone_dst;
+							if (((axis_delta < 0.0f) ? -1 : 1) == direction) {
+								ebone_src = ebone;
+								ebone_dst = ebone_iter;
+							}
+							else {
+								ebone_src = ebone_iter;
+								ebone_dst = ebone;
+							}
+
+							ebone_src->temp = ebone_dst;
+							ebone_dst->flag &= ~(BONE_SELECTED | BONE_TIPSEL | BONE_ROOTSEL);
+						}
+					}
+				}
+			}
+		}
+	}
+
+	/*	Find the selected bones and duplicate them as needed, with mirrored name */
+	for (ebone_iter = arm->edbo->first; ebone_iter && ebone_iter != ebone_first_dupe; ebone_iter = ebone_iter->next) {
+		if (EBONE_VISIBLE(arm, ebone_iter) &&
+		    (ebone_iter->flag & BONE_SELECTED) &&
+		    /* will be set if the mirror bone already exists (no need to make a new one) */
+		    (ebone_iter->temp == NULL))
+		{
+			char name_flip[MAX_VGROUP_NAME];
+
+			BKE_deform_flip_side_name(name_flip, ebone_iter->name, false);
+
+			/* bones must have a side-suffix */
+			if (!STREQ(name_flip, ebone_iter->name)) {
+				EditBone *ebone;
+
+				ebone = duplicateEditBone(ebone_iter, name_flip, arm->edbo, obedit);
+
+				if (!ebone_first_dupe) {
+					ebone_first_dupe = ebone;
+				}
+			}
+		}
+	}
+
+	/*	Run though the list and fix the pointers */
+	for (ebone_iter = arm->edbo->first; ebone_iter && ebone_iter != ebone_first_dupe; ebone_iter = ebone_iter->next) {
+		if (ebone_iter->temp) {
+			/* copy all flags except for ... */
+			const int flag_copy = ((int)~0) & ~(BONE_SELECTED | BONE_ROOTSEL | BONE_TIPSEL);
+
+			EditBone *ebone = ebone_iter->temp;
+
+			/* copy flags incase bone is pre-existing data */
+			ebone->flag = (ebone->flag & ~flag_copy) | (ebone_iter->flag & flag_copy);
+
+			if (ebone_iter->parent == NULL) {
+				/* If this bone has no parent,
+				 * Set the duplicate->parent to NULL
+				 */
+				ebone->parent = NULL;
+			}
+			else {
+				/* the parent may have been duplicated, if not lookup the mirror parent */
+				EditBone *ebone_parent =
+				        (ebone_iter->parent->temp ?
+				         ebone_iter->parent->temp : ED_armature_bone_get_mirrored(arm->edbo, ebone_iter->parent));
+
+				if (ebone_parent == NULL) {
+					/* If the mirror lookup failed, (but the current bone has a parent)
+					 * then we can assume the parent has no L/R but is a center bone.
+					 * So just use the same parent for both.
+					 */
+					ebone_parent = ebone_iter->parent;
+				}
+
+				ebone->parent = ebone_parent;
+			}
+
+			/* Lets try to fix any constraint subtargets that might
+			 * have been duplicated
+			 */
+			updateDuplicateSubtarget(ebone, arm->edbo, obedit);
+		}
+	}
+
+	transform_armature_mirror_update(obedit);
+
+	/* Selected bones now have their 'temp' pointer set,
+	 * so we don't need this anymore */
+
+	/* Deselect the old bones and select the new ones */
+	for (ebone_iter = arm->edbo->first; ebone_iter && ebone_iter != ebone_first_dupe; ebone_iter = ebone_iter->next) {
+		if (EBONE_VISIBLE(arm, ebone_iter)) {
+			ebone_iter->flag &= ~(BONE_SELECTED | BONE_TIPSEL | BONE_ROOTSEL);
+		}
+	}
+
+	/* New bones will be selected, but some of the bones may already exist */
+	for (ebone_iter = arm->edbo->first; ebone_iter && ebone_iter != ebone_first_dupe; ebone_iter = ebone_iter->next) {
+		EditBone *ebone = ebone_iter->temp;
+		if (ebone && EBONE_SELECTABLE(arm, ebone)) {
+			ED_armature_ebone_select_set(ebone, true);
+		}
+	}
+
+	/* correct the active bone */
+	if (arm->act_edbone && arm->act_edbone->temp) {
+		arm->act_edbone = arm->act_edbone->temp;
+	}
+
+	ED_armature_validate_active(arm);
+
+	WM_event_add_notifier(C, NC_OBJECT | ND_BONE_SELECT, obedit);
+
+	return OPERATOR_FINISHED;
+}
+
+/* following conventions from #MESH_OT_symmetrize */
+void ARMATURE_OT_symmetrize(wmOperatorType *ot)
+{
+	/* subset of 'symmetrize_direction_items' */
+	static EnumPropertyItem arm_symmetrize_direction_items[] = {
+		{-1, "NEGATIVE_X", 0, "-X to +X", ""},
+		{+1, "POSITIVE_X", 0, "+X to -X", ""},
+		{0, NULL, 0, NULL, NULL}
+	};
+
+	/* identifiers */
+	ot->name = "Symmetrize";
+	ot->idname = "ARMATURE_OT_symmetrize";
+	ot->description = "Enforce symmetry, make copies of the selection or use existing";
+
+	/* api callbacks */
+	ot->exec = armature_symmetrize_exec;
+	ot->poll = ED_operator_editarmature;
+
+	/* flags */
+	ot->flag = OPTYPE_REGISTER | OPTYPE_UNDO;
+
+	ot->prop = RNA_def_enum(
+	        ot->srna, "direction", arm_symmetrize_direction_items, -1,
+	        "Direction", "Which sides to copy from and to (when both are selected)");
+}
+
 /* ------------------------------------------ */
 
 /* previously extrude_armature */

source/blender/editors/armature/armature_intern.h

@@ -72,6 +72,7 @@ void ARMATURE_OT_shortest_path_pick(struct wmOperatorType *ot);
 
 void ARMATURE_OT_delete(struct wmOperatorType *ot);
 void ARMATURE_OT_duplicate(struct wmOperatorType *ot);
+void ARMATURE_OT_symmetrize(struct wmOperatorType *ot);
 void ARMATURE_OT_extrude(struct wmOperatorType *ot);
 void ARMATURE_OT_hide(struct wmOperatorType *ot);
 void ARMATURE_OT_reveal(struct wmOperatorType *ot);

source/blender/editors/armature/armature_ops.c

@@ -66,6 +66,7 @@ void ED_operatortypes_armature(void)
 
 	WM_operatortype_append(ARMATURE_OT_delete);
 	WM_operatortype_append(ARMATURE_OT_duplicate);
+	WM_operatortype_append(ARMATURE_OT_symmetrize);
 	WM_operatortype_append(ARMATURE_OT_extrude);
 	WM_operatortype_append(ARMATURE_OT_hide);
 	WM_operatortype_append(ARMATURE_OT_reveal);