/** Internal node in a Quadtree
*/
class QuadTreeInternal extends QuadTree{
  QuadTree ne, nw, sw, se; //children
  double midx, midy;

  QuadTreeInternal(Point3d pne, Point3d pse, Point3d pnw, Point3d psw,
		   QuadTree ne, QuadTree se, QuadTree nw, QuadTree sw){
    super(pne,pse,pnw,psw);
    this.ne = ne;
    this.se = se;
    this.nw = nw;
    this.sw = sw;
    midx = (pne.x() + pnw.x())/2;
    midy = (pne.y() + pse.y())/2;
  }
	
  QuadTree insert(Point3d p){
    super.insert(p);
    if (p.x() > midx) {
      if (p.y() > midy) {
	ne = ne.insert(p);
      } else {
	se = se.insert(p);
      }
    } else {
      if (p.y() > midy) {
	nw = nw.insert(p);
      } else {
	sw = sw.insert(p);
      }
    }
    return this;
  }

 /** check all points in this quadtree to see if they're inside candh
            case where we're looking for points above (greater z) */
  protected void findup(double zint) {
  	ne.find();
  	se.find();
  	nw.find();
  	sw.find();
  }
  	

  /** check all points in this quadtree to see if they're inside candh
            case where we're looking for points above (greater z) */
  protected  void finddown(double zint){
  	findup(zint);
  }

  void dump(int indent){
    super.dump(indent);

    out(indent,midx);
    out(indent,midy);
    out(indent,"ne");
    ne.dump(indent+2);
    out(indent,"se");
    se.dump(indent+2);
    out(indent,"nw");
    nw.dump(indent+2);
    out(indent,"sw");
    sw.dump(indent+2);
  }
			

}