function getBox(obj: THREE.Object3D): THREE.Box3
{
    if (obj.hasOwnProperty("geometry"))
    {
        let geom = obj["geometry"];
        geom.computeBoundingBox();
        return geom.boundingBox;
    }
    else
    {
        if (obj.children.length > 0)
        {
            let box;
            for (var index = 0; index < obj.children.length; index++)
            {
                var element = obj.children[index];
                let box2 = getBox(element);
                if (box2)
                {
                    if (box)
                    {
                        box.union(box2);
                    }
                    else
                        box = box2;
                }
            }
            return box;
        }
        return null;
    }
}