public static void toTangentsWithParity(IrMesh mesh) {
        for (IrPolygon polygon : mesh.polygons) {
            for (IrVertex vertex : polygon.vertices) {
                toTangentsWithParity(vertex);
            }
        }
    }
Applies smoothing groups to vertex normals. XXX not implemented!

@param mesh ignored
@return null
jme3-plugins/src/main/java/com/jme3/scene/plugins/IrUtils.java