>  >   Sorry, I did a poor reading, and for the images I assumed too 
> quickly your
>  > problem was just the ultra-bright media... trying with your code on 
> the last
>  > message, I see that using extinction 0 gives the effect you are 
> looking for.
> 
> Yes, that's quite logical... I tried it, and it at least yielded roughly 
> the result I want to achieve in the long run! Thank you for the tip... 
> perhaps I'll up the extinction value to, let's say, 0.1 or 0.15, as the 
> unlit side is of course somewhat darker than the lit side, irrespective 
> of light filtering through...

Just for completeness' sake: From a theoretical point of view, the 
"extinction" parameter is no good for your application, as it only 
accounts for light that fails to be transmitted due to being scattered 
away. As a consequence, only the scattered colors are attenuated 
accordingly.

This is good for modelling media in which the scattering is primarily 
due to diffraction or other interference effects (i.e. very small 
particles, like molecules or very fine dust), but does not properly 
model media containing larger objects in which the scattering is 
primarily due to reflection, as in that case all wavelengths will be 
obstructed, whether they are reflected (and therefore scattered) or not.

I guess in the case of the Saturn rings, reflection will be the primary 
scattering effect, so it should be modeled using...

- an absorbing media to account for the shadowing effect
- a scattering media to account for the reflected light

The scattering media, in this case, should indeed have "extinction 0", 
as the extinction component is already accounted for by the absorbing media.


Christoph

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