Recently, I have been looking for techniques to make volumetric fog on some Y position level of the game world. But all I have found are some fog made by using particle system or built-in engine fog that doesn't really fit what I'm looking for.
In my case, I need a fog that is both efficient and dense. It should be all over the gameworld, but obviously, for performance reasons, it can be rendered only as a part of a camera or shader and look like it's moving though it's just an illusion. I could set a particle system if it's the best choice, attach it to the camera and make it move.
So the main question still stays - how can I implement a volumetric fog that is both dense and performs efficiently?
As a particular engine I'm using, it's Unity.
As an example what I mean, here is the link to a game with the effect I'm looking for: Astromike