Get your head back in the fog with Digieffects Atmosphere plug-in.

  Now you can add true 3 dimensional atmospheric falloff in After Effects.  No more adding semi-transparent solids between your 3D layers to simulate fog or haze.  With Atmosphere you get true three dimensional fog that gets denser as your layer stretches into the distance.

Use it with multiple layers separated in Z space or rotate your 3D layers  on the X or Y axis and watch them fade off into the distance.

This effect can be added to individual layers for fine control of the effect on each layer or applied to an entire comp so the effect applies the same parameters to all layers.  You have control over where the fog starts and ends as well as how dense it is and how quickly it falls off.

The only other way to simulate this effect is with elaborate particle generators which add render time and empty your wallet.  At $49.00 this plug-in is a must have for any designer or compositor.