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smellenbergh wrote:
>
> J. Grimbert <jgr### [at] atos-group com> wrote:
[SNIP]
> >
> > In cones.c, just replace the 0.0 by Cone->dist in Compute_Cone_BBox
>
> > That's all Folks!
> > I have put an explanation with a picture on
> > http://www.altern.org/grimbert/pov/index.html
> > --
> > J. Grimbert
> Well, we tried it and it certainly is an improvement. However, the
> bounding boxes are not as tight as they might be.
Could you please elaborate on that ?
I personaly don't see how you could have a thighter bounding box
without clipping into the cone.
> You can see this right away if you turn on the 'draw vista buffer'
> option.
I would like, but draw vista buffer is not available on
the default unix port. And I do not have a Window compiler...
>
> Please, try our fix and notice the difference. We have been waiting a
> long time for someone to fix it. Our method is a fix but it should be
> possible to make it easier with less memory use.
IMNSHO, your fix just try to perform the same bounding box as mine, but
take the things too last and therefor is far more complicated and
request more memory.
> Ok, we include our message from a while ago so you can try this. It
> involves a bit more than replacing 0.0 by Cone->dist :-) but please try
> it and see the difference.
>
Reading it again, and from the mathematical point of view, I do not see
the difference in the bounding box.
You start with a bounding box of 2x2x1 and scale it by "len" in the
axial
direction, thus giving a 2x2xlen bounding box.
I start with a bounding box of 2x2x(1-tmpf/tlen) and scale it by "tlen"
in
the axial direction thus giving a 2x2x(tlen-tmpf) bounding box.
As tlen == tmpf + len
(therefore tlen - tmpf == len)
I have the same bounding box as your fix.
How, Wait... I just see it now. I should also decreased the 1.0 from
the Cone->dist .
I had only half-corrected it.
> If you can and are willing to do so, try to fix it even more.
I will update my page...
> It makes
> quite a difference if you have images with lots of those cones.
I agree, especially for truncated cones, it does have a significant
impact on rendering time (the std 3.1g waste most of the time hitting
a bounding box and then looking for the intersections with the cone.
>
> Best regards,
> Smellenbergh
>
Have a nice day.
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