public void display()
    {
        win2.pushMatrix();
        // translate to coordinates of center of top of t1
        int height;
        int h1 = myWall.getT1().getHeight();
        int h2 = myWall.getT2().getHeight();
        if (x < Animation.WALL_WID / 2)
        {
            height = h1;
        }
        else if (x > Animation.WALL_LEN + Animation.WALL_WID / 2)
        {
            height = h2;
        }
        else
        {
            height = h1 + (int)((h2 - h1) * (x - Animation.WALL_WID/2.0) / Animation.WALL_LEN); 
        }
        win2.translate(myWall.getT1().getX() + Animation.WALL_WID/2, height, myWall.getT1().getZ() + Animation.WALL_WID/2);

        // rotate so current is running left to right.
        if (myWall.getT1().getZ() > myWall.getT2().getZ())
        {
            win2.rotateY(win2.PI / 2);
        }
        else if (myWall.getT1().getX() > myWall.getT2().getX())
        {
            win2.rotateY(win2.PI);
        }
        else if (myWall.getT1().getZ() < myWall.getT2().getZ())
        {
            win2.rotateY(3 * win2.PI / 2);            
        }
        // draw sphere at appropriate height (tower or wall height)
        win2.translate((float)x, -RADIUS, 0);
        win2.sphere(RADIUS);

        // draw Ski lifts to push balls through batteries
        if (myWall.getPosEnd() != null)     // if this wall is a Battery...
        {
            //Draw elevator (box) behind sphere
            if ( myWall.getT2().equals(myWall.getPosEnd()) )  // if positive Terminal is on the right...
            {
                win2.translate(-RADIUS, 0, 0);
            }
            else        // if positive terminal is on the left...
            {
                win2.translate(RADIUS, 0, 0);
            }
            win2.box( 5, (int)(1.5 * RADIUS), (int)(1.5 * RADIUS) );
        }
        win2.popMatrix();
    }