Wasn't it Bill Pragnell who wrote:
>Are there any circumstances under which manually bounding mesh objects is more
>efficient than using the automatic bounding hierarchy? Since it is possible to
>turn off the feature and do it manually I'd guess yes, but I can't find out how
>it might be the case.
>
>Can anyone shed any light on this for me?

The usual situations where manual bounding can be better are those where 
the intersection or difference of two large objects produces a small 
result. If you have prior knowledge about the size of the result, you 
can set the bounds to match it, whereas POV has no such prior knowledge 
and has to set the bounds much larger.

Another factor is that the automatic bounding slabs are always aligned 
with the axes. So if you had a mesh object of a thin plate which was 
tilted at 45 degrees there might be some gain from bounding it with a 
thin box which was also tilted at that angle. Mesh objects render so 
efficiently anyway that the gains would be unlikely to be very 
significant unless the mesh object has a large number of large polygons.

-- 
Mike Williams
Gentleman of Leisure

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