Reduced view distance
The King of the Hill mission allows a player to modify the view distance within the game using the player menu. Additionally, there's a feature to drastically reduce the view distance with a shortcut:
Shift + F2.
When enabled, the view distance is reduced to some 100 meters, which is especially useful within close quarter combat in cities or situations, where enemies far away matter less. Reducing the view distance may increase the FPS of the game.
When the reduced view distance feature is enabled, an icon in the HUD at the left middle side of the screen is visible.