/** @return */
public WB_Coord getFaceNormal() {
if (_halfedge == null) {
return null;
}
// calculate normal with Newell's method
HE_Halfedge he = _halfedge;
final WB_Vector _normal = new WB_Vector();
HE_Vertex p0;
HE_Vertex p1;
do {
p0 = he.getVertex();
p1 = he.getNextInFace().getVertex();
_normal.addSelf(
(p0.yd() - p1.yd()) * (p0.zd() + p1.zd()),
(p0.zd() - p1.zd()) * (p0.xd() + p1.xd()),
(p0.xd() - p1.xd()) * (p0.yd() + p1.yd()));
he = he.getNextInFace();
} while (he != _halfedge);
_normal.normalizeSelf();
return _normal;
}
