> Alain<aze### [at] qwertyorg>  wrote:
>> Why is your sun and planets both at coordinate 0?
>
> The planet[s] should be in a union that's translated at the end.

Then, during the devlopment phase, place your sun some distance away. 
That way, the radiosity contribution will be visible and not totaly 
hiden by the direct illumination.

>
>> With 3.6.1, there was a bug in radiosity: The recursion level had to
>> take transparent surfaces into consideration. You have 4 athmospheric
>> layers and recursion_level default to 3. Then, you have two sets of
>> layers plus the actual surface, for a total of 9.
>
> Excellent! I think you've hit upon it, Alain! Thank you.

Another reason to use version 3.7...

>
>> That said, I realy think that you should use only one athmospheric shell
>> containing only scattering media. You then modulate the density of that
>> media as needed, using the spherical pattern scalled to the radius of
>> the athmonsphre or some custom function.
>
> Oh, I didn't realize we had a spherical pattern before! I will definitely
> investigate.
>
>> fade_power 10? for your athmosphere?
>> A realistic fade_power is 1 for substances to use linear fading, or 1001
>> to use the exponential formula.
>> Test without fading gives beter results.
>> It's fade_power 2 for a fading light_source.
>
> This was to replace extinction, because I wasn't artistically satisfied with
> realistic results. Still willing to work on that; I probably just didn't have it
> configured correctly.
>
> Thanks a lot, everyone! I might post more on this later, but my initial question
> has been answered.
>
>

Just a note about the spherical pattern:
It's centered at <0,0,0>
It's value is 1 (rgb<1,1,1>) at the origin and drop to zero at a radius 
of 1, then stay to zero everywhere.

There is also the onion pattern. It's a spherical gradient pattern. 
Start at zero at the origin and climb up to 1.

In your scene, you have a merge of all your athmospheric shells 
containing a single media.
You need to give an individual shell to each planet, apply the spherical 
pattern then place them into position.
Adjust the colour_map for the pattern to be 1 at the planetary surface 
and drop to zero at the very top of the shell.
Something like:
color_map{[Planet_Radius/Athmosphere_radius rgb 1][0 rgb 0]}

It's normal to take some artistic liberties when you model something 
that is physicaly impossible. That quadruple planet just can't exist, 
the center planet may survive, but the 3 moons would be ript apart by 
the gravitational gradient and degenarate into a massive ring of 
debrits. Think Saturn's rings, but about 10000 to 1000000 times denser.



Alain

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