public bool Intersects(FastBounds b)
        {
            var gap =
                (max_x < b.min_x || b.max_x < min_x) ||
                (max_y < b.min_y || b.max_y < min_y) ||
                (max_z < b.min_z || b.max_z < min_z);

            return(!gap);
        }
 public void Encapsulate(FastBounds fb)
 {
     Encapsulate(fb.min_x, fb.min_y, fb.min_z);
     Encapsulate(fb.max_x, fb.max_y, fb.max_z);
 }