public static Plane constructNormalizedZPlane(final double x,final double y){
  if (Math.abs(x) < MINIMUM_RESOLUTION && Math.abs(y) < MINIMUM_RESOLUTION)   return null;
  final double denom=1.0 / Math.sqrt(x * x + y * y);
  return new Plane(y * denom,-x * denom,0.0,0.0);
}

public static Plane constructNormalizedZPlane ( final double x , final double y ) { if ( Math . abs ( x ) < MINIMUM_RESOLUTION && Math . abs ( y ) < MINIMUM_RESOLUTION ) return null ; final double denom = 1.0 / Math . sqrt ( x * x + y * y ) ; return new Plane ( y * denom , - x * denom , 0.0 , 0.0 ) ; }
construct a normalized plane through an x - y point and including the z axis . if the x - y point is at ( 0 , 0 ) , return null .
