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On Thu, 22 Jul 1999 00:03:16 -0400, Nathan Kopp <Nat### [at] Kopp com> wrote:
>The big problem is that POV encloses the origin of the cone in the cone's
>bounding box. The origin is the place where the cone narrows down to a
>single point. So although your cone is only 30 units long or so, POV
>makes the bounding box big enough to fit a 1000 unit long cone (or some
>other really big number).
Hi, Nathan. It's been many years but I once did an impromptu comparison to
see how much difference manual bounding could make on simple shapes or CSG
objects. I experimented with ever tighter-fitting boxes and spheres to see
what the rendering speed improvement could yield. I also used other shape
primitives since any of them can be used for bounding purposes, though the
box and sphere are the most highly optimized, according to the docs section
4.5.6.2. For example, is it advantageous to bound a cone with a
tight-fitting cone as opposed to a box?
It made a difference back then with an older version of POV-Ray but I
don't know how relevant or practical this would be today, using v3.1g. This
was before Dieter implemented the vista and light buffers as a speed-up.
While sometimes the improvement was dramatic I do recall that there was an
apparent (and not unexpected result) of diminishing returns as the bounding
shapes were dimensioned closer and closer to the object size.
--
Alan
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