What does -dark do?

[Satan_Fang]

I tried out a command called -dark and compared it using shots but I never noticed anything different, does this command change the map in anyway?

[obsidian]

It uniformly darkens areas between brush edges and lightmap seams. It’s hard to notice. -dirty enables ambient occlusion and works more realistically, so I recommend using -dirty over -dark, or you can enable both just for kicks.