On Thu, 18 Mar 2004 09:35:50 -0800, Darren New <dne### [at] sanrrcom>
wrote:

>As the manual explains  {X inverted} is object X with the inside and 
>outside reversed - a "negative" X.  difference{X,Y} is the same as 
>intersection{X, Y inverted}. So, by itself, Y fills your entire scene, 
>other than where the cylinder or whatever actually is. *That* is what 
>you have to bound for efficiency. In an intersection, POV knows that it 
>can bound Y inverted by X. But if X is a union that's unnecessarily big, 
>it can't really tell where Y needs to get cut off. POV can't 
>automatically tell that in
>   intersection ( union (A,B,C), X inverted )
>X really only affects C, So if A fills your whole screen, and X really 
>only chops part of C out, rays hitting A still have to check against X.

Yes, I see it, now.  So, using your example above:

 intersection( union(A, B, C), X inverted)

How would I optimize the bounding boxes in this situation?  The
problem lies with X's bounding box, and I need to shrink it down
considerably.  Right?

>Maybe that helps?  Or have I explained something wrong?

I think this helps greatly.  Thanks!

- How

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