Margus Ramst <mar### [at] peakeduee> wrote ...

> 2) Very high quality (many rays, low error_bound) will eliminate (or
obscure?)
> the dark patches, but other freaky things occur (see for yourself). Maybe
> related, maybe not.

High numbers here:

>         count 1200
>         error_bound 0.05
>         low_error_factor 0.1

Ok, now you've put the error bound TOO low.  When it is this low the
following happens:
For each pixel, POV tries to find previously computed values and use them.
But it fails because the error bound is so low that none of the previous
values work.  So, instead, it takes shoots out another 1200 rays and gathers
again.  Then it uses this single estimate to color that pixel.  Then it does
it again for the next pixel.  This totally defeats the entire purpose of
reusing samples.  And it adds noise to the radiance estimate, sonce now you
have quickly-changing radiosity (a different estimate for each pixel)
instead of gradually-changing radiosity.

So I guess what I'm saying is that, when it comes to UVPov's radiosity, that
'too much of a good thing...' saying does apply.

The following gives a pretty good radiance estimate (at least it looks
pretty good to me).  Note the decreased low_error_factor:  this causes just
about all gathering to occur during the preview passes and almost none to be
done in the final pass, which leads to a much better radiance estimate
(albiet a slower render).  You could probably go down to an error_bound of
about 0.9 or 0.8 (not much less than that, though) but then increase that
low_error_factor back up to maybe 0.4.  Also note the increased
nearest_count (more things to average generally means a better estimate).

(low_error_factor could probably go down to 0.2, and nearest_count probably
up to 15 or 20, but when that doesn't change the scene much and really slows
things down.  Also, with that low of a low_error_factor*error_bound
combination, you could just skip straight to the 2x2 preview pass)

    radiosity{
        brightness 2
        count 150
        error_bound 1
        gray_threshold 0
        low_error_factor .3
        minimum_reuse 0.015
        nearest_count 10
        recursion_limit 1
        max_sample 10
        adc_bailout .01/10
    }


-Nathan

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