protected override void end_stroke()
        {
            base.end_stroke();

            activeChange.SaveCurrentNormals();
            if (EmitChangeF != null)
            {
                ModifyVerticesMeshChange change   = activeChange.ExtractChange();
                UpdateVerticesChange     soChange = new UpdateVerticesChange(Target, change);
                EmitChangeF(soChange);
            }
            else
            {
                activeChange.Reset();
            }
        }