I prefer more complicated, slower methods of doing this sort of thing. In fact I
wanted to try out that very thing you suggest. I would use a radial pigmentment
map that blends between the two. I'm sure it's inelegant and very slow, though.

Josh

Chris Jeppesen wrote:

> I am working on a planet earth model, and I found this cool map of the
> cities at night (Thanks Jon Berndt! for the reference). I am using it as a
> mostly transparent shell 0.000001 bigger than my earth image map sphere.
>
> Now, the question. I of course want to only see the city lights on the unlit
> side of earth. The easy unelegant way is to cut the sphere in half and make
> sure that the city lights are applied only opposite the sun, but that
> requires a knowledge of where the sun is, and more calculations than I care
> to do.
>
> Then I came up with a briliant (I thought) Idea: Set the ambient of the
> shell to 0.5, then the diffuse to -0.5. My thinking is that a negative
> diffuse setting means that the more light you hit it with, the darker it
> gets. So a full light hitting normal to this shell should result in a total
> effect of 0.5 Ambient+(-0.5 Diffuse)=0 light.
>
> This kinda works, but not as well as I had hoped. It seems as though diffuse
> is constrained to be >0. Does anyone know if this is true? Does anyone have
> any better ideas?
>
> Chris Jeppesen

--
Josh English -- Lexiphanic Lethomaniac
eng### [at] spiritonecom
The POV-Ray Cyclopedia http://www.spiritone.com/~english/cyclopedia/

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