public void setZero() {
		xx = 0.0;
		yx = 0.0;
		zx = 0.0;
		xy = 0.0;
		yy = 0.0;
		zy = 0.0;
		xz = 0.0;
		yz = 0.0;
		zz = 0.0;
		xd = 0.0;
		yd = 0.0;
		zd = 0.0;
	}
public void setZero ( ) { xx = 0.0 ; yx = 0.0 ; zx = 0.0 ; xy = 0.0 ; yy = 0.0 ; zy = 0.0 ; xz = 0.0 ; yz = 0.0 ; zz = 0.0 ; xd = 0.0 ; yd = 0.0 ; zd = 0.0 ; }
Sets all elements to 0, thus producing and invalid transformation.