The Science of Fog
2012.03.05 - 
Counter-Strike players need to quickly identify their targets, so it’s important that those targets stand out. But as environments have become more richly detailed, it has gotten harder to separate a player from the background. This affects players by slowing their searches for targets, and can be the difference between life and death.
Atmospheric haze (‘fog’) is one of the tools we use to solve this problem. It reduces the visual impact of the distant environment, and when the appropriate amount is used in a map, players become far more distinguishable:
Spot the terrorist and then mouse over the image to add fog.
Did you spot both terrorists?
In today’s update, we have adjusted the levels of haze in de_train. The adjustment balances the need to make out players at long distances with the benefit of separating players from the background. We’re going to keep de_train the map to play as we collect more data to measure the impact of this change.
It’s true that eliminating haze would allow snipers to see very distant targets more clearly. However, aside from helping in that isolated case, removing it entirely would slow searches in the vast majority of player interactions. Counter-intuitive as it may seem, a little fog can help you see much more clearly.
