The truth about fog

What do you need to know about fog? You know it as the condensation of water vapour in the air at low heights. That’s the scientific explanation. Little do you know there’s a more … evil reason behind it’s existence…

So you can’t see squat in front of you!

That quality of obscuring objects serves a more important purpose in computer games and 3D renderings. Because of finite calculations, outdoor scenes need to be “contained”. The trick is to use clipping planes, a near plane and a far plane, to restrict the amount of visible information.

Due to this restriction, objects that are really far, but you know is there, aren’t rendered. This has the effect of objects appearing suddenly when you move forward in the scene. As you move, objects meet the visible requirement and are thus rendered.

To help assuage this effect, we add fog to the scene. Objects that aren’t visible can now be partially explained by the presence of fog. At least to your brain.

That was to improve the aesthetics of the rendered scene. In some games, particularly of the horror genre, fog’s main purpose is to hide practically everything from sight. If you can’t see a monster, but you can hear heavy breathing and footsteps, the scare factor goes up (hopefully).

This is illustrated with the use of fog in the game Silent Hill 2.

So now you know the truth about fog.