"Tim Nikias" <JUSTTHELOWERCASE:timISNOTnikias(at)gmx.netWARE> wrote:
> That's not possible with a reasonable PC. You're asking for actual
> light-scattering according to wavelengths, which POV-Ray doesn't do unless
> you use photons, and using photons to light up the sky is... well... out of
> reach with current standard desktop PCs.

Yes, I was exaggerating a little bit when asking for a real sky... I
understand that any simulation suppose some limitations. Let's see if my
understanding of "Photons" is correct:

We assume our scene is made of an atmosphere a sphere (earth) and a light
source. In that case the only elements we lose when rendering without
photons are some contrasts (in the media and on the sphere) due to
refraction of light in the atmosphere. Isn't it?

So, for a first simulation of earth atmosphere we could forget refraction
effects. I think it is reasonable since as far as I know the main physical
phenomena that determine the color of the sky are scattering and
absorbtion, but not refraction.

Now we could simulate the atmosphere using a first media with Rayleigh
scattering (chosing a higher coefficient in the blue)... and a second media
that would simulate the effects (absorbtion and diffusion) of aerosols...
maybe we need a third one...!

Limitations of these simulations are "single scattering", very simplified
wavelenght dependencies of scattering and absorbtion as well as simplified
atmosphere structure.

Please tell me if I missed something. At that point I still think we can
obtain somthing which is not too far from the real sky? I'm working on it,
and I'm learning some more about Povray, thanks Tim for your very
instructive website.

[Reynald] - www.guidevtt.com

Post a reply to this message