Gert  Van den Eynde <gvd### [at] hotmailcom> wrote:
> Hi all,
>
> Sorry for asking a question that maybe has come up already. I'm trying to
> model the first drafts of our house and I was wondering how I could best
> model the light coming from our sun (at different times during the day and
> year)? Do I put a light-emitting sphere far away? What color? What
> radiosity settings would I best use? I would like to see (in a relative
> way) how light/dark some corridors and rooms are compared to other rooms or
> outside.
>
> All tips are more than welcome!
>
> gert

This is a real pain. I *still* can't quite get things properly lit from
windows without burning things out a bit. That said, here's what I suggest:

Use sunpos.inc (came with povray) to get the sol's position, given a time
(along with lat and lon, etc)

Use Jaime Vivres' lightsys (http://ignorancia.org/lightsys.php) to get the
color of the sun, as filtered by the atmosphere. Then use the associated
skylight include (comes with lightsys) to make a sky that looks right for
the sun's position.

Now use radiosity, as if you were using HDR, so something like:

radiosity {
      pretrace_start 0.08
      pretrace_end   0.04
      count 200
      nearest_count 10
      error_bound 0.15
      recursion_limit 2
      low_error_factor 0.5
      gray_threshold 0
      minimum_reuse 0.015
      brightness 1.0
      adc_bailout 0.01/2
}

Leave the sun pretty dark, and make the sky pretty hazy, and you get fairly
good results. I'll post a couple of example images (of a model of a room of
my house, so I know they're not too far from reality).

Good luck!

-S

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