Jörg 'Yadgar' Bleimann nous illumina en ce 2009-04-12 10:12 -->
> High!
> 
> While waiting for help with the rail segments connection problem, I 
> reactivated a very old project put to hibernation back in 1999: a 
> full-fledged POV Solar System, this time with astronomically correct 
> elliptical orbits of planets and moons and a procedural starry 
> sky_sphere gleaned from star data from a German astronomical atlas 
> ("Karkoschka"), as I found a promising tutorial on computing planetary 
> positions on the website of a Swedish amateur astronomer
> ( http://www.stjarnhimlen.se/comp/tutorial.html )
> 
> I programmed several camera modes, one of them with the camera pointing 
> towards a customizable location stated in geographical coordinates on 
> Earth. As long I left my Earth sphere standing upright in space, this 
> works fine - but how do I correct the camera's orientation for Earth's 
> axial tilt (rotate <23.4333, 0, 0>?
> 
> I quickly understood that the tilt angle multiplied with the sine of the 
>  longitude (with western longitudes being positive, eastern ones 
> negative) had to be added to/subtracted from the original latitude - but 
> how is the longitude adjusted afterwards?
> 
> See you in Khyberspace!
> 
> Yadgar
If you start ON the ecliptic, or Earth's orbital plane, at a point based on the 
Earth's position at the time of an equinox, you don't have to compensate. In 
this case, the rotation is only around a single axis.

Another aproach:
Don't tilt the earth, DO tilt everything else! The end visual result will be 
exactly the same.

As the camera is selected with a variable, you can use that same variable to 
tilt, or not, your "universe".

-- 
Alain
-------------------------------------------------
I couldn't repair your brakes, so I made your horn louder.

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