Weight Paint: Make multi-paint & mirror work as if bone selection was symmetric

The simplest way of handling mirroring in multi-paint is creating a
uniform symmetric selection and relying on existing symmetric weights
to direct changes to the appropriate vertex groups. This already works
if mirror bones are selected manually, and can be made easier to use
by doing it implicitly.

1 files changed, 24 insertions, 0 deletions

diff --git a/source/blender/blenkernel/intern/object_deform.c b/source/blender/blenkernel/intern/object_deform.c
index e823f87468d..38391c84d29 100644
--- a/source/blender/blenkernel/intern/object_deform.c
+++ b/source/blender/blenkernel/intern/object_deform.c
@@ -596,6 +596,30 @@ bool *BKE_object_defgroup_selected_get(Object *ob, int defbase_tot, int *r_dg_fl
 	return dg_selection;
 }
 
+/* Marks mirror vgroups in output and counts them. Output and counter assumed to be already initialized.
+ * Designed to be usable after BKE_object_defgroup_selected_get to extend selection to mirror.
+ */
+void BKE_object_defgroup_mirror_selection(
+        struct Object *ob, int defbase_tot, const bool *dg_selection,
+        bool *dg_flags_sel, int *r_dg_flags_sel_tot)
+{
+	bDeformGroup *defgroup;
+	unsigned int i, i_mirr;
+
+	for (i = 0, defgroup = ob->defbase.first; i < defbase_tot && defgroup; defgroup = defgroup->next, i++) {
+		if (dg_selection[i]) {
+			char name_flip[MAXBONENAME];
+
+			BKE_deform_flip_side_name(name_flip, defgroup->name, false);
+			i_mirr = STREQ(name_flip, defgroup->name) ? i : defgroup_name_index(ob, name_flip);
+
+			if ((i_mirr >= 0 && i_mirr < defbase_tot) && (dg_flags_sel[i_mirr] == false)) {
+				dg_flags_sel[i_mirr] = true;
+				(*r_dg_flags_sel_tot) += 1;
+			}
+		}
+	}
+}
 
 /**
  * Return the subset type of the Vertex Group Selection