From a mappers perspective, hl2s lighting is the same old pain in the ass like in old hl.
Valve said, that vis will take only a couple of minutes to compile, but i dont think so....
Engines ala Doom3 and stalker will be better... only set the light parameters, klick the savebutton and start...
Think about it people.
Back in won times, you had to download patches around 90mb and more at once to be able to play the game.
I think its better to download small patches from time to time.
+
HL was on of the first games with continuous leveldesign (unreal).
Some people will fall down very hard when they think hl2 will get 98% or 100% etc.... :rolleyes:
I don't think hl2/css/ has a day-night cycle.
Simply because the used bsp-tree with its pre rendered vis and rad has 1 defined lightstyle and thats it.
You could fake it with tuning down the brightness, some dark sprites/fog and the change of the animated sky.
Realtime Lightcycle ala...