"clipka" <nomail@nomail> wrote:
> "Samour" <nomail@nomail> wrote:
> > Now for Rayleigh the phase function is close to what is found in the literature
> > multiplied by some normalizing constant (the equation in the literature is
> > 0.75*(1.0 + Sqr(alpha)), POV-Ray uses 0.799372013 instead of 0.75), and for
> > Henyey-Greenstein it is identical.
>
> I just checked the math, and the factors seem to be wrong indeed; I came up with
> the following factors:
>
> - Rayleigh scattering:     3/4
> - "Mie Hazy" scattering:   1/2
> - "Mie Murky" scattering: 33/83
>
> (For the "Mie" formulae, my attempt at symbolic integration had me come up with
> 1 and 66/83, respectively, but numeric integration gave me values matching the
> above quotients, so I guess I just goofed by a factor of 2.)
>
> Henyey and isotropic scattering seem to be properly normalized.
>
>
> (Normalization appears to be for a spherical integral of 4 pi, not 1, or else
> I'm mistaken.)


OK thanks. That helps a lot.

Now if I understand correctly, the original source for these equations is:
Principles of digital image synthesis By Andrew S. Glassner.

I still don't understand how you came up with the normalization factors for the
Mie scattering though. Sorry for being such a bother.

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