Adding rain or snow to your map is extremely simple. It's not totally necessary for game play, but does add a very nice feel to a map. Below are snapshots of the rain and snow effects in the game.
Note: Adding weather effects (especially rain) can degrade the frame rate of some systems. You probably don't want to use it on maps with huge open areas.
Figure 1: Rain with splashes and ripples on water surfaces
Figure 2: Falling snow
How to add weather effects
Just follow these steps...
Put an info_doddetect entity in your map if you don't already have one
Open up the info_doddetect entity's properties and select Weather Type
From the drop-down menu on the right, select which type of weather effect you would like in your map (see illustration below).
Figure 3: Entity properties for info_doddetect and weather
Icing on the cake
Here are a few suggestions for consistency to make your map look and feel even better with weather effects...
Use textures that match, such as the snow textures from Zalec and Kalt in maps with snow
Use skies that match the weather. If it's raining or snowing, it's going to be cloudy!
To minimize frame rate issues, try to not make huge open areas in maps. Large areas will involve large numbers of particles to create weather effects, and will cause frame rate degradation for most players.
Add background ambience sounds to your map which match the weather. There are several ambience sounds that fit well. The "dodambience4.wav" file (in sound\ambience folder) has the sound of battle combined with a muffled rain sound. The file "dodambience5.wav" has a similar sound, but adds in a faint wind sound. If you want just the windy sound (effective in a snow map), use "windy.wav" in the same folder.
This article was originally published on the Valve Editing Resource Collective (VERC). TWHL only archives articles from defunct websites. For more information on TWHL's archiving efforts, please visit the TWHL Archiving Project page.