"jute" <nomail@nomail> schrieb im Newsbeitrag
news:web.415865be6aa6ed1cf834c8120@news.povray.org...
> Hi folks,
Hi,
i think the problem is, that radiosity sometimes misses
your sun when taking radiosity-samples and sometimes it
hits your sun. The problem is the low count-value.
the count-value determines the number of sample-rays that
are shot for each radiosity-calculation in random
directions of the hemisphere. Each ray has to 'observe'
a part of the hemisphere that gets larger the lower
your 'count' is. If your sun has a small solid angle
when viewed from your room it's possible that it falls
between two (or more) samplerays and therefore is
completely missing in the calculation. So you should
choose the count-value high enough that no significant
ambient lightsources are missed in the sampling.
A good rule of thumb is:
  count >= 3*(r/R)^2
where r is the distance of the lightsource to the lit
area and R is the radius of the (sphere-shaped)
lightsource.
So if in your example you want to model the sun in POV
realistically you should use a minimum count of
  3*(1,5*10^11m / 7*10^8m)^2 = 140000
So it's rather utopistic to realize that in POV-Ray...
Perhaps it's better to use a pointlight to make the
sunlight and just use a small ambient-value like 1
to let your sun appear reasonable bright.

I hope i didn't disappoint you too much..

Thies

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