Environmental effects add atmosphere to a level ... literally. Competitive players might want to turn them off at the earliest opportunity, but everyone else should appreciate the added ambience.
Enemy Territory provides support for three main types of environmental effect; Precipitation, Distance Fogging and Foliage. In addition to this there are other, more subtle effects you can use in order to convey atmosphere to the player.
Precipitation (See sand storms)
There are two types of precipitation currently available: Snow, and Rain. Both use the same worldspawn key, atmosphere. The individual keys in the value strings provide the following settings:
|T||RAIN||Type of effect (sypports 'RAIN' or 'SNOW')|
|B||5 10||Base times (X seconds, or between X and Y seconds)|
|C||1 1||Time to move from base to gust (X seconds, or between X and Y seconds)|
|G||0 2||Gust times (X seconds, or between X and Y seconds)|
|BV||0 100||Base vector (x and y units/sec)|
|GV||0 100||Gust vector (x and y units/sec)|
|W||1 2||Weight of particle (X, or from X to Y depending on base/gust position)|
|H||0||If a particle gets created more than this amount of units above a player drop the creation spot down to viewheight H (this parameter is optional)|
|D||300 300||Number of particles (baseparticles / gustparticles) - max 3000|
Two maps included with Enemy Territory used Rain and Snow effects. The atmosphere worldspawn keys used for each is as follows:
Radar: "T=RAIN,B=5 10,C=0.5,G=0.5 2,BV=50 50,GV=200 200,W=1 2,D=2000"
Railgun: "T=SNOW,B=5 10,C=0.5,G=0.3 2,BV=20 30,GV=25 40,W=3 5,D=2400"
It's possible to create sleet or hail effects by varying the weight (W) of the particles, or to produce a light rain or snow shower by decreasing the density (D) of the particles.
If your level has a very high sky, you may find your snow or rain fades out to nothing before it has chance to hit the ground. To fix this you can adjust the height it starts at and cap it artificially using the height (H) parameter.
For variable weather, the base (B, BV) and gust (G, GV) parameters can be used to adjust the precipitation over time. Most of the parameters in the atmosphere key can be given dual values for base and gust, as shown in the table above. By using markedly different values for each, and setting a large time to gust (C) value, you can create weather that increases or decreases over the course of a match.