POV-Ray : Newsgroups : povray.general : user-defined media density function : Re: user-defined media density function Server Time
31 Jul 2024 22:12:25 EDT (-0400)
  Re: user-defined media density function  
From: Eric Buddington
Date: 25 Aug 2006 21:15:01
Message: <web.44ef9f702dcd370abef64010@news.povray.org>
"Nekar" <ger### [at] rpmmagcoza> wrote:
> "Eric Buddington" <ebu### [at] wesleyanedu> wrote in message
> news:web.44ee43068f5cf101abef64010@news.povray.org...
> > I'm trying to model the Earth's atmosphere (as a sphere) using scattering
> > media.
> > The atmosphere's density follows a e^(height) type function.
> > The available wave types don't seem to include this. I've played with
> > spherical mapping and poly and cubic wave types,but it's unsatisfactory so
> > far.
> >
>
>
> Does this include the troposphere, stratosphere, mesosphere, ozone, etc? Or
> is it just a simple function?

It uses the barometric formula
(http://en.wikipedia.org/wiki/Barometric_formula)
to calculate air density (assuming constant temperature, so it's just
Ae^B(height)), and uses Raleigh (type 4) scattering on that density. I then
scale it to earth size, and squash it to fit the Earth's ellipsoidosity
(That's a word. Really. I bet.)

It seems a little too thin overall, probably because there's a fair amount
of absorption and isotropic scattering in the troposphere that I haven't
added yet.

Clouds would be cool to add, but I think very computationally expensive to
do well (this is video, so I can't afford even 15 minutes per image)

-Eric


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