Hi Thorsten,
One more tidbit of info on phase of the moon. The phase of the moon is
proportional to the relative location of the sun and the moon in the sky;
more specifically the angle between them. For example, a full moon will be
rising precisely when the sun is setting -- in this case they are nearly
180 degrees opposite in the sky and you see the entire reflection of the
sun light off the moon. When the moon is straight up in the sky at the
same time the sun is setting, it will be a 1/2 moon. When the moon is
almost in the same place in the sky as the sun (near zero degrees) then you
either don't see the moon, or you may see an extremely thin sliver. You
may recall seeing a very thin sliver of moon just above the horizon right
after sunset -- the sun and moon are very close together in the sky and
it's really hard to see the moon until the sun drops below the horizon.
FlightGear positions the sun and moon in their correct 'relative' positions
in the sky, and then we illuminate the moon sphere from the sun, and that
automatically gives us the correct phase/orientation of the moon in the sky
visually. So that's a pretty cool way to get the correct moon in the sky
(I think), we don't do anything fancy, just copy nature's design. :-)
I don't know off hand if the direction (vectors) of sun & moon illumination
are available in the property tree. But if they were or could be made
available, then your task is simply to compute the angle between these two
vectors. That angle is proportional to the amount of the moon that is
visibly illuminated to us. 180 degrees = full moon, 90 degrees = 1/2 moon,
0 degrees = no moon. Of course these values are rarely 180 or 0 degrees
exactly -- that would correspond to an eclipse which so far has been beyond
the scope of our rendering methods to properly display. But now with
Rembrandt maybe we can begin to cast the earth's shadow onto the moon?
What do you think Fred? :-)
Curt.
On Fri, Nov 9, 2012 at 7:08 AM, Durk Talsma wrote:
> Just a quick note for now, because I've got a lecture coming up in about
> 30 minutes...
>
>
> If you need any information about the moon's position and/or phase, just
> let me know. It should be trivial to extract these values from the
> ephemeris code.
>
> Cheers,
> Durk
>
>
> On 09 Nov 2012, at 13:25, Renk Thorsten wrote:
>
> >> Interesting, looks good. So effectively it glows...
> >
> > Not really - unlike glowing stuff, it is actually obscured by cloud
> cover for instance.
> >
> > * Thorsten
> >
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--
Curtis Olson:
http://www.atiak.com - http://aem.umn.edu/~uav/
http://www.flightgear.org - http://gallinazo.flightgear.org
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