CovenantSpy-->Yes, it is very possible to change the darkness. However, the majority of the mods you saw where it looked darker were probably done the "cheater's" way. This way is by darkening all of the bitmaps that are displayed on the level (rocks, vehicles, MC, grass, etc.) using photoshop. The problem with doing it this way is that it will LOOK dark, but light sources will not show up very well (I.E: Headlights, flashlights, and beacons won't cast light much if at all, due to the way the lighting in HALO works)
However, there is a more advanced way to achieve the night-time effect and have it be completely realistic. Ang88 believed that the actual lighting was encoded into the BSP as an element (The BSP is the actual level's model, texture maps, surfaces, collision model, and a few other things all compressed into one "file" so to speak).
This, while it may be true on some other games, is not true in HALO. The lighting in HALO .map files is created by ARGB (Alpha-Red-Green-Blue) bitmaps. These bitmaps are layered over the entire level to lighten and darken areas of the map (I.E: The huge cliff shadows in Blood Gulch are made by having a darker ARGB bitmap applied over those areas. When an object such as the hog enters this shadow, it too has the same ARGB bitmap applied to it, therefore making it become darker). So shadowed or dark areas have darker ARGB bitmaps applied over them and lighter areas (such as those in direct "sunlight") have lighter ARGB bitmaps applied over them.
So, by correctly darkening certain ARGB bitmaps and re-injecting them, you can effectively make the entire level's lighting a lot lower, creating a night-time level. The only thing that may be needed after doing this is to change the fog's color to black, or it will show up all too well and crap up the level's visuals. By darkening a map this way, you allow the headlights, flashlights, and other light sources still work correctly. This is because THEIR light is also controlled by ARGB bitmaps, and if you do not darken them, they will still correctly lighten the textures they are applied to, retaining their correct effect.
*whew*....hope this explained it well enough for you...I don't know if you'll understand all of it, but I tried my best...now I'm off to continue on my latest night-mod.
