/** Bounded box clipped by extent
 * (crude, could fix, see Realistic Ray Tracing by Shirley p. 22)
 * @author: Phil Gage
 */
class Box extends AbstractObject {

    Extent extent;
    BoundedPlane sides[] = new BoundedPlane[6];
    Intersection tempIntersection = new Intersection ();

    /** Create box */
    Box (Extent extent, Color color) {
        super(color);
        this.extent = extent;
        sides[0] = new BoundedPlane (
            extent.max, new Vector3 (0,0,1), extent, color);
        sides[1] = new BoundedPlane (
            extent.max, new Vector3 (1,0,0), extent, color);
        sides[2] = new BoundedPlane (
            extent.min, new Vector3 (0,0,-1), extent, color);
        sides[3] = new BoundedPlane (
            extent.min, new Vector3 (-1,0,0), extent, color);
        sides[4] = new BoundedPlane (
            extent.min, new Vector3 (0,-1,0), extent, color);
        sides[5] = new BoundedPlane (
            extent.max, new Vector3 (0,1,0), extent, color);
    }

    /** Returns positive if ray intersects box */
    double intersect (Ray ray, Intersection intersection) {
        double dist, t = Constants.INFINITY;
        intersection.obj = null;
        for (int i=0; i<6; i++) {
            dist = sides[i].intersect (ray,tempIntersection);
            if (dist > 0.0 && dist < t) {
                t = dist;
                intersection.set(tempIntersection);
                intersection.obj = this;
            }
        }
        if (intersection.obj == null)
            return 0.0;
        else
            return t;
    }

    Extent getExtent () {
        return extent;
    }
}