This scene demonstrates many of the effects that raytracing can produce. The checkerboard is
made of blocks and holes, so you can see rays terminate when they hit something. The near ball is transparent,
and you can see the ray bend as it enters and leaves the object. The far ball is reflective;
watch the rays bounce off of it. You can see the Light Ray cast toward the light when it hits
something to determine if it is in shadow or not.