CoGr@Ohm

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Layered Fog:

That is fog with a certain density $\mu$ that stretches up to a particular height level $h$. Everything below that level $h$ is foggy and attenuated with the factor $w$:

$w = 1-e^{-\mu d}$

But what is $d$, which corresponds to the length a viewing ray travels through the fog layer? This can be computed as the length $d$ of a ray cast into the scene until it hits the top level plane of the layered fog.

With that ray length $d$ the factor $w$ is used to linearily interpolate the scene with a white background:

$I' = wI + (1-w)1$

The above is usually implemented via a fragment shader plus blending.

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