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On 21 Sep 1999 09:22:29 -0400, Nieminen Juha wrote:
>Ron Parker <par### [at] fwi com> wrote:
>: You forget that if it's not around the object, it shouldn't matter to the
>: ray-intersection routine (obviously in practice it works in such a way that
>: vampire objects are possible, but that's a side-effect that could easily
>: disappear with better optimization.) And rest assured that finite objects
>: have bounding boxes whether or not such boxes are specified in the script;
>: that's how the min_extent and max_extent keywords in the superpatch work.
>
> How does it calculate the bounding box of an object like this?
>
>intersection
>{ sphere { x*1000, 1001 }
> sphere { -x*1000, 1001 }
>}
It calculates the intersection of the bounding boxes of the individual
spheres, so it would bound by box{<-1,-1001,-1001>,<1,1001,1001>}. I
didn't say it was always correct; in fact, I've mentioned before that
min_extent and max_extent aren't always entirely accurate for every
object. If you specify your own bounding volume, of course, it uses
that one if it's smaller than the computed one.
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