I just tweaked my "Coding Fog Addendum" tutorial to incorporate the new code I've added...
The fog was, originally, switchable -- on or off. I've added "fade on" and "fade off" times, so that instead of just blinking in and out of existence, it actually fades in and out.
(I got it working so I could try out my "lab11_heathaze" idea, but at some point I shall have to design a level with fog in mind... ;-))
Edit: Of course, it wasn't until the drive home that it occurred to me that my revised version will probably do extremely bad things to network latency -- something I probably won't get to test until next Monday now...
sigh
Edit II: After all that, I've decided that Lab11: HeatHaze looks pretty damn good with fog, but the whole fading-in thing (which works fine) is not so great for the level. And yes, it does play havoc, so I'll need to revise the tutorial again sometime...