env_fog
env_fog is a point entity available in the following 
GoldSrc games or engine branches:
Counter-Strike, 
Counter-Strike: Condition Zero, 
Condition Zero Deleted Scenes and 
Deathmatch Classic. This entity is used to cover the map in fog. Most Counter-Strike FGDs do not come with this entity listed, it has to be manually added in the FGD to be used in Hammer.
Key values
- Start distance
(startdist)<integer> (only in) - This value defines how far away from the player the fog will start. At this range, the fog is completely transparent.
- End distance
(enddist)<integer> (only in) - This value defines how far away from the player the fog will end. At this point, the fog becomes 100% opaque.
- Start distance
(fogStartDistance)<integer> (only in, & ) - Distance where the fog begins to appear.
- Stop distance
(fogStopDistance)<integer> (only in, & ) - Distance where the fog ends to appear.
- Fog density
(density)<integer> (only in, & ) - Density of the fog.
- Fog Color (R G B)
(rendercolor)<color255> - This property allows you to set the color of the fog using an "R G B" value. For example, for blue fog you could use "0 0 255".
Flags
- [
1] : Fog Affects Skybox (only in, & )
