» Sat May 28, 2011 12:16 pm
It's all in the weather settings. There are settings for day, sunset, night and sunrise. These settings control the amount of light/the color for the various parts that make up the weather. There is one for fog, for ambient light, for sunlight, for sun, for cloud textures, for the sky, the horizon, the stars etc. If you set ambient light and sunlight to really dark (RGB settings around 20 or lower) the player will need a torch to see anything.
If you have an interior where you can't see the sky all you need to change is ambient and sunlight (and maybe fog if it's a very large interior with a low fog setting). Ambient light is the overall light level. It doesn't look very nice as it will light up everything by the same degree. Sunlight is a directional light that comes from the direction where the sun (or moon(s) at night) is.
If you can see the sky you need to test a lot to make everything fit together (bright horizon with dark lower sky layer will look weird for example). But you can watch weather in the CS render window by pressing the sky button so you don't need to go in game to see what it looks like.