// set an outer proposed boundary for parent object(s)
// allows the ray-tracer to do a quick check on the Bounding Shape,
// and if outside, it skips checking this object, which can speed
// up overall rendering of complex shapes.  Note that this
// is not a 100% guaranteed clipping shape... use the
// clipped_by statement for that.
bounded_by { box { -(x+y+z) +(x+y+z) }
