> The relavent POV code is below.  Does anything look awry?
>    media {
>       intervals 15  //more needed? -> 100
>       //ratio 0.5
>       samples 2,6
>       method 3

Well, there are three methods for media. I don't know anything about method
1, since POV 3.5 I've just been using methods 2 and 3 (mainly method 3).
With method 2, you want to use an amount of intervals which return
sufficient results, and have to take care that "samples" uses the same value
for min and max, otherwise, the result might look grainy.
With method 3, you want to use only one interval, but varying values for min
and max for "samples". I'd try method 2 for this volume first though.

Now, given the amount of data in your volume, I'd say that you're using way
too few intervals. What might happen is that when the ray travels through a
dense region, it might sample before and after the bright region. Since
those two samples are nearly identical, the adaptive-algorithm assumes that
between those two samples no significant changes occur, and hence, the
bright spot is lost.

Another note regarding your clipping-theory: when colors get clipped in
POV-Ray, they get clipped to an upper or lower boundary, I've never heard of
values getting clipped via some modulo function (e.g. when clipping between
0 and 1, 1.2 would turn out as 0.2).

Regards,
Tim

-- 
"Tim Nikias v2.0"
Homepage: <http://www.nolights.de>

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Thanks very much, this fixed my problem!  It still confuses me how the
clipping effect could result from insufficient sampling, but oh well..  I
would expect it to simply make the data look more blurry.

Now I can get to my real renderings involving radiosity.  Expect more
questions. :)

Thanks,
Eric

"Tim Nikias v2.0" <#macro timnikias (@) #local = "gmx.net" #end> wrote in
message news:40b123c4$1@news.povray.org...
> > The relavent POV code is below.  Does anything look awry?
> >    media {
> >       intervals 15  //more needed? -> 100
> >       //ratio 0.5
> >       samples 2,6
> >       method 3
>
> Well, there are three methods for media. I don't know anything about
method
> 1, since POV 3.5 I've just been using methods 2 and 3 (mainly method 3).
> With method 2, you want to use an amount of intervals which return
> sufficient results, and have to take care that "samples" uses the same
value
> for min and max, otherwise, the result might look grainy.
> With method 3, you want to use only one interval, but varying values for
min
> and max for "samples". I'd try method 2 for this volume first though.
>
> Now, given the amount of data in your volume, I'd say that you're using
way
> too few intervals. What might happen is that when the ray travels through
a
> dense region, it might sample before and after the bright region. Since
> those two samples are nearly identical, the adaptive-algorithm assumes
that
> between those two samples no significant changes occur, and hence, the
> bright spot is lost.
>
> Another note regarding your clipping-theory: when colors get clipped in
> POV-Ray, they get clipped to an upper or lower boundary, I've never heard
of
> values getting clipped via some modulo function (e.g. when clipping
between
> 0 and 1, 1.2 would turn out as 0.2).
>
> Regards,
> Tim
>
> -- 
> "Tim Nikias v2.0"
> Homepage: <http://www.nolights.de>
>
>


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