/** * Returns the quality of this tet. * Quality is a number between 0 and 1, inclusive. * Quality equals 1 for equilateral tets. * Quality equals 0 for degenerate tets with co-planar nodes. * @return tet quality. */ public double quality() { if (_quality<0.0) _quality = quality(_n0,_n1,_n2,_n3); return _quality; }