"Margus Ramst" <mar### [at] peakeduee> wrote...
> janger wrote:
> >
> > Does anyone know of a way to model the sky using media, scattering etc
to
> > create a blue sky? I'm not sure if it's possible. Basically I don't want
to
> > use a sky sphere to mimic the sky, but try and create a 'true'
atmosphere
> > which looks blue because of light scattering, and so I can make a 'sun'
> > which is way out in the distance, in scale with reality, and shines
through
> > the atmosphere as happens in nature.
>
> Wavelength-dependant scattering is not possible in POV (at least not yet).
But
> you should be able to simulate it well enough with regular scattering (or
even
> just emitting & absorbing) media, coloured appropriately.

There seems to be a misconception here.  POV can do "almost" wavelength
dependent scattering.  The closest thing to wavelength in POV is color.  And
POV can _easily_ do color-dependent scattering.  That is as close as you'll
get until POV supports an arbritary division of the color spectrum, instead
of breaking it up into only three components (i.e. instead of using a
3-component RGB color vector, you might use a 7-component ROYGBIV color
vector).

That said, wavelength-dependent scattering can be simulated quite well using
POV.  It can even be simulates so well that simply moving the sun to the
horizon will produce nice shades of red, orange, and yellow for a sunset.
Different scattering colors can be used to achieve different sunset colors,
such as pinks and purples (this could be used to simulate different
atmospheric conditions, such as humidity and temperature).  Please see
"Scattering media sky" that I just posted in p.b.s-f.  Note that the
original code was created by somebody else, I only tweaked it.

-Nathan

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