public RectangleRn WrappingRectangle() { 
     Line line = new Line(points[0], points[1]);
     RectangleRn wr = line.WrappingRectangle();
     for (int i=1; i < points.Length; i++) {
         line = new Line(points[i], points[(i+1) % points.Length]);
         wr.Join(line.WrappingRectangle());
     }
     return wr;
 }