public SidedPlane(Vector p,Vector v,double D){
  super(v,D);
  sigNum=Math.signum(evaluate(p));
  if (sigNum == 0.0)   throw new IllegalArgumentException("Cannot determine sidedness because check point is on plane.");
}

public SidedPlane ( Vector p , Vector v , double D ) { super ( v , D ) ; sigNum = Math . signum ( evaluate ( p ) ) ; if ( sigNum == 0.0 ) throw new IllegalArgumentException ( "Cannot determine sidedness because check point is on plane." ) ; }
construct a sided plane with a normal vector and offset .
