Wasn't it Peter Duthie who wrote:
>Will the bounding box of a CSG intersection be the intersection of the 
>bounding boxes of it's components, or will it be the union of them?  Or 
>something else entirely?
>
>The reason I ask is that I'm taking relatively small 'slices' of basic 
>constructs using an intersection with a thin box, and I want to know if 
>the resultant bounding box will be the optimal area where the bounding 
>box of the construct intersects with the bounding box of the box used to 
>slice it up.  If not, I can manually calculate the bounding box and 
>apply it fairly easily, I'd just rather not do that if POV already does 
>it for me.

It's easy enough to check. You can get a sort of 2d representation of
your bounding boxes by adding +MB0 +UD to the command line. (+UD does
all the work, but for a simple test scene +MB0 ensures that bounding
gets enabled).

For a 3d representation of a bounding box you can code it like this

// Create the thing
#declare THING =  intersection {
  box {0,1}
  sphere {1,0.5}
}

// Display the thing
object {THING pigment {rgb 1}}

// Display semitransparent bounding box
box{
  min_extent(THING),max_extent(THING)
  pigment {rgbt <1,0,0,0.5>}
}  

In my tests, POV was using the intersections of the bounding boxes of
the components.

-- 
Mike Williams
Gentleman of Leisure

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