NOTE: THIS WORKS PROPERLY ONLY ON NIGHT MAPS/NIGHT SCENEBUILDS
you want really neat global lighting but due to Source’s limitations putting a shitload of lamps around either kills your PC or messes up the shadows. solution? YOU GO GREENSCREEN ON THAT ASS
well okay black/whitescreen but you get it
as an example i’ll use my latest piece of work
the base pic without the lighting:
now, here’s the lighting (minus the siren lights from the police spinner down on the ground) in a separate layer
and with colours that were added afterwards
i take the base pic with only the light bulb lighting enabled, then disable the fog and colour everything - EVERYTHING - completely black, without changing the materials (i do make transparent glowing stuff, such as omni tools and holograms, invisible though). then i trigger different sets of lamps, one after another, taking pics between each push of a button.
then i color all the $selfillum stuff that couldn’t be blacked out in-game (such as the neon signs) black in GIMP, blend the different pics together and slap this new lighting layer on the base pic with the blending mode set to Screen (not sure how this works in photoshop(p. much any blending mode, that ignores black and takes only the bright parts into account, should work)), and finally color that layer with colors that fit the pic, eg outside lighting is blueish, light coming from doorway is yellowish etc.
here are colored versions of some of the layers i used
i came up with this idea after realizing that I can isolate easily with black/white layers if I use black fog and white materials with mat_fullbright. “wait, what if i isolate the LIGHTING too???” and here we are