public int compare(Spatial o1, Spatial o2) {
public int compare(SceneElement o1, SceneElement o2) {
        public int compare(Spatial o1, Spatial o2) {            float d1 = distanceToCam(o1);            float d2 = distanceToCam(o2);            if (d1 == d2)                return 0;            else if (d1 < d2)                return 1;            else                return -1;        }