The post over at Hivewire that moogal mentioned sounds like one of mine. I remember bagginsbill guiding me through the creation of the realistic falloff depth cue shader on the CGBytes Poser material room forum (the node knows?) and posting a screenshot of the complete shader over there.

But that forum seems to have disappeared.

I'm fairly sure that I have all the information including an MT5 on my laptop, but that's at home whereas I'm not. Not sure how long you'll have to wait though, so posting a screenshot of the atmosphere shader you downloaded as bagginsbill suggests may be the quickest.

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The 3Dcheapskate* occasionally posts sensible stuff. Usually by accident. And it usually uses Poser 11, with units set to inches. Except when it's using Poser 6 or PP2014, or when its units are set to PNU or something else.
*soon only to be available in two flavours -  DAZ and Renderosity