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Christoph Hormann wrote:
> Jim McElhiney wrote:
> >
> > Hi, Jim here.
>
> Hello and welcome!
>
Thanks! This is my first post here. Last time I said anything was in the
GO GRAPHICS forum at Compuserve.
(yawn! Rip van Winkling on this for a few years now...)
In fact I'm now a retired guy and I've been working on the radiosity
code lately, fixing the ancient and dreaded blotchiness problem,
and other bugs.
(turns out the blotchiness really is mostly a bug all along).
Not even sure how the POV team works these days,
i.e., who keeps the ball for making new official patches, or
(for that matter) whether or not anyone is interested in my bug fixes.
I like your examples. Frankly, I like any image made using that
code, as I was very proud of it. (not Catholic, so it ain't a sin!)
If you build your own versions, and if you're interested, I can suggest a
VERY quick hack (not a real bug fix) which will fix one big error.
In radiosit.cpp, around line 844 where it calls ot_index (there is only
one call), the second parameter is (and always has been) wrong.
(it is correct for top level light collection only, but does not allow
for the situations where the error bound gets adjusted on the fly,
which happens with recursion depth and with low-radiosity-contribution
points)
I'm working on the exact expression, (depends on the implemention
of other things, such as recursion limit depth), but if you just take the
value
there and multiply it by 3 or 4 your images will look better, by
avoiding some discontinuities in shading.
This will make results more correct and *very* slightly slower.
(it will make searches in the octree a bit slower, by considering
a few extra nodes, but that's pretty quick integer stuff, not like
tracing more rays).
Rgds
Jim
>
> > I actually wrote the offending line of code.
>
> Thanks for the detailed explanation, especially considering that is has
> been quite some time since you wrote that code (which is probably at the
> same time one of the most loved and most hated parts of POV-Ray...).
>
> I have made some tests with the different methods some time ago:
>
> http://www-public.tu-bs.de:8080/~y0013390/simpov/docu04.html
>
> and it seems there are quite significant differences although you can't
> really say one method is better than the other in general as it seems.
>
> Christoph
>
> --
> POV-Ray tutorials, include files, Sim-POV,
> HCR-Edit and more: http://www.tu-bs.de/~y0013390/
> Last updated 17 Jun. 2003 _____./\/^>_*_<^\/\.______
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