I finally manage to clean the mess on my hard drive and prepare the spotlight effect build with fog.

The effect was good when I was trying it with JO (compiled by sof2map).

Unfortunately I was unable to repeat the same effect today for JA (q3map2). I don't know what's wrong with the fog but the effect looks nice only from one side. I have tried different fog options with no success. I'm sorry but I was unable to solve this problem. I don't know if it's related to my poor ATI drivers, q3map2 compiler, fog shader, game engine or something else.

good:

http://www.mslaf.com/tutorials/spotlight1.jpeg)
http://www.mslaf.com/tutorials/spotlight2.jpeg)

bad:

http://www.mslaf.com/tutorials/spotlight3.jpeg)

the source map and shader can be downloaded from here:

http://www.mslaf.com/tutorials/spotlight.zip)

I'll have a go at it later today, but did you try to mss with alphaMod volumes yet? Should be pretty fun on this one. :)

I was thinking about it but I'm not very familiar with this feature;)

It's quite easy, check the thread by seven_dc at SD, it explains the basics.

I already have the shaderlab_1337 sample, just need some time to analyze it.