Am 28.11.2017 um 02:26 schrieb omniverse:

> Wish you good luck adjusting the color bands of the atmosphere. I couldn't get
> it any better myself after a couple hours so I gave up trying anymore. I think
> it's because of the gradient y mixed with spherical warp, not really sure.
> Just that every time I moved the index values it changed in ways (both altitude
> AND color!) I wasn't able to get correct like I wanted.

My guess is that it's mostly due to POV-Ray using a simple RGB colour
model. In certain situations this is prone to making colours drift
towards the primaries (red, green, blue) or their complementary colours
(cyan, violet, yellow).

This effect is particularly strong wherever colour is affected by the
distance traveled through a medium through attenuation, such as in fog,
absorbing/scattering media (purely emissive should be ok), fading
interior, or subsurface light transport. Look up "dichromatism" for an
explanation of this phenomenon (an extreme example being pumpkin seed
oil, which may appear bright green when spilled, but bright red in a
bottle; no way we can simulate this with POV-Ray's current RGB model).

To properly model dichromatism, we would need spectral rendering. While
this would add more knobs to tweak (after all you'd have to toy with
many more colour channels than just R, G and B), and thus may not make
it particularly /easy/ to achieve truly realistic results, it would at
least make it /possible/.

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