[Radiance-general] Sun too close to zenith
Gregory J. Ward
gregoryjward at gmail.com
Wed Dec 7 23:39:28 CET 2005
Hi Rob,
I'm not exactly sure why I put this in there, it was so long ago. I
may have simply been duplicating someone else's algorithm, or I may
have found problems related to the sun at zenith. The whole sky
distribution is normalized to the zenith value, so having the sun too
near could be a problem, or it might have been paranoia on my part.
You can try removing lines 218-225 in gensky.c and recompiling without:
if (!overcast && altitude > 87.*PI/180.) {
fprintf(stderr,
"%s: warning - sun too close to zenith, reducing altitude to 87
degrees\n",
progname);
printf(
"# warning - sun too close to zenith, reducing altitude to 87 degrees
\n");
altitude = 87.*PI/180.;
}
Try a few data points where the sun is at the zenith and see what
happens.
-Greg
> From: Rob Guglielmetti <rpg at rumblestrip.org>
> Date: December 7, 2005 1:59:46 PM PST
>
> Hi all,
>
> I'm using Francesco Anselmo's "radmap" script to generate some
> annual skies for a fairly low latitude, and for a portion of the
> summer gensky throws me a warning: "sun too close to zenith,
> reducing altitude to 87 degrees". This adjustment creates a slight
> "bump" in the summertime corner of the analemma when you view a
> hemispherical fisheye projection of the annual sun positions. (The
> sun positions are being generated by the script, which is getting
> its info from an epw weather file.)
>
> What is the cause for gensky relocating my suns to 87 degrees?
>
> - Rob Guglielmetti
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