On 27 Apr 1999 12:41:04 -0500, Nieminen Mika <war### [at] cctutfi> wrote:
>  This has an interesting consequence: The bounding box doesn't need to be
>surrounding the object it's bounding; it's enough that from the point of
>view of the camera it completely covers the bounded object on screen.

You neglect reflected and shadow rays, but other than that this explanation 
seems reasonably correct.  As a result, you could use this effect to create 
a "vampire object" with no reflection and no shadow (bound it with a small
sphere around the camera), or an invisible object that casts a shadow (bound
it with a small sphere around the light source.)  Don't forget the -UR on 
the command line.
 
It's also worth noting that if you specify two or more bounding objects, the 
ray must hit all of them before it will be tested against the real object, 
so if you want to bound by multiple disjoint spheres, make sure to union 
them first.

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