"Mike Williams" <mik### [at] econymdemoncouk> wrote in message
news:JopK2DARl2d+Ewq### [at] econymdemoncouk...
> Wasn't it Matti Karnaattu who wrote:
> >If object is made using CSG and boxes then is it true that avoiding
> >intersection and difference speeds up rendering?
>
> Yes, but in many cases you can get most of the speed back if you can
> apply tight manual bounding. POV can't work out, in advance, which parts
> of the objects remain after some bits are removed, so it creates an
> automatic bounding box that contains the union of the objects.
>

Is this right?

Surely with:

difference{
    object{A}
    object{B}
}

and

intersection{
    object{A}
    object{B}
}

They could be bound by the object{A} bounding box, rather than the bounding box
of the union of A and B?

In the case of the intersection, you could also switch to the bounding box of B
if that was smaller than A's.

I thought that that was what happened (although I don't know if the final
paragraph is implemented).

Actually, what *DOES* happen with intersections? Does POV look for the smallest
bounding-box, or does it just use the box of the first object in the list? If
the latter, then it would presumably make sense to list your smallest object
first.

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