John VanSickle wrote:

> Perhaps one reason that pre-dawn and early dawn scenes look much darker 
> than what you're used to seeing in the real world is the fact that our 
> eyes adjust to darkness and brightness to bring all scenes to the 
> middle.  If things are too dark, our eyes adjust to make everything 
> brighter.


fwiw I concur. In my own raytracer I got close, but getting consistent 
coloration between different ground camera angles (pointing along the 
ground, then pointing up at the sky's zenith, etc.) was wonky. Can be 
tweaked for stills without reflections, but the moment you add a lake or 
ocean, the colors would be wrong because the zenith sky would be partly 
reflected while the camera is aiming at the horizon sky.

The problem turned out to be the color model. In RGB, it's hard or 
perhaps intractable; in CIE it's easy because the color units are more 
directly mapped to actual radiation wavelengths which the 
scattering/absorption equations prefer, and tonemapping to handle eye 
dark/light adaptation is easy too.

Ray

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