1 files changed, 23 insertions, 7 deletions

diff --git a/source/blender/editors/mesh/editmesh_tools.c b/source/blender/editors/mesh/editmesh_tools.c
index d1ff06ec213..e22dab2f3c8 100644
--- a/source/blender/editors/mesh/editmesh_tools.c
+++ b/source/blender/editors/mesh/editmesh_tools.c
@@ -26,6 +26,11 @@
  * ***** END GPL LICENSE BLOCK *****
  */
 
+/** \file blender/editors/mesh/editmesh_tools.c
+ *  \ingroup edmesh
+ */
+
+
 /*
 
 editmesh_tool.c: UI called tools for editmesh, geometry changes here, otherwise in mods.c
@@ -5199,27 +5204,38 @@ static int blend_from_shape_exec(bContext *C, wmOperator *op)
 	Key *key= me->key;
 	EditMesh *em= BKE_mesh_get_editmesh(me);
 	EditVert *eve;
-	KeyBlock *kb;
-	float *data, co[3];
+	KeyBlock *kb, *refkb= NULL;
+	float *data, *refdata= NULL, co[3];
 	float blend= RNA_float_get(op->ptr, "blend");
 	int shape= RNA_enum_get(op->ptr, "shape");
-	int add= RNA_int_get(op->ptr, "add");
+	int add= RNA_boolean_get(op->ptr, "add");
 	int blended= 0;
 
 	if(key && (kb= BLI_findlink(&key->block, shape))) {
 		data= kb->data;
 
+		if(add) {
+			refkb= BLI_findlink(&key->block, kb->relative);
+			if(refkb)
+				refdata = refkb->data;
+		}
+
 		for(eve=em->verts.first; eve; eve=eve->next){
 			if(eve->f & SELECT) {
 				if(eve->keyindex >= 0 && eve->keyindex < kb->totelem) {
-					VECCOPY(co, data + eve->keyindex*3);
+					copy_v3_v3(co, data + eve->keyindex*3);
 
 					if(add) {
-						mul_v3_fl(co, blend);
-						add_v3_v3(eve->co, co);
+						/* in add mode, we add relative shape key offset */
+						if(refdata && eve->keyindex < refkb->totelem)
+							sub_v3_v3v3(co, co, refdata + eve->keyindex*3);
+
+						madd_v3_v3fl(eve->co, co, blend);
 					}
-					else
+					else {
+						/* in blend mode, we interpolate to the shape key */
 						interp_v3_v3v3(eve->co, eve->co, co, blend);
+					}
 
 					blended= 1;
 				}