"Philipp" <pov### [at] phipracom> wrote:
....
> I then would like to determine when (date and time of the day) the reflected
> sunlight falls on a certain area of the floor (or objects). It need not be a
> realistic rendering - I just want to determine the days in the year when the
> reflected sunlight hits an object that sits on the floor.
>
> To my understanding, this should be possible by using photon mapping, and
> then trying to make a fast-motion video from it. Is that correct, and is it
> feasable for, say, a hobby programmer to do this within two working weeks?
>
> (Is there some module or code-snippet for automatically calculating the
> sun's position, given geographical position and date/time?)
>
To answer your questions: yes, yes, and yes.  POV-Ray comes with sunpos.inc,
a macro to do just what you would like (2.7.20.6 sunpos.inc).   Two weeks
should be sufficient.  Pay particular attention to coordinate handedness.
You'll need a separate piece of software to make the animation.  Here's a
link to the sunpos.inc doc page:

http://www.povray.org/documentation/view/3.6.1/498/

I like to use SunPos() to show the seasonal solar exposure and penetration
of structures so as to minimize heat gain in the summer and maximize it in
the winter.  I throw a bunch of intensity- and color-coded 'suns' in the
sky (red for summer 'cooling days', and blue for winter 'heating days').
The resulting red-magenta-blue hues illuminating the surfaces of the
structure indicate where wanted and unwanted solar radiation is
intercepted.  Passive solar performance should be good when exterior
surfaces appear red (and are well-insulated there) and the surfaces of
internal thermal masses are blue.

Hope this helps.

-David

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