+ slope + ", xIntersection: " + xIntersection;
+ slope + ", xIntersection: " + xIntersection + ", isClip: " + isClip;
  public String toString()  {    return "Edge: " + x0 + ", " + y0 + ", " + x1 + ", " + y1 + ", slope: "           + slope + ", xIntersection: " + xIntersection;  }