How do You create Fog/Volumetric Light?
 

Hey Guys. I am working on a scene which needs a Fog effect. Specfically, I have a warehouse scene where a square opening exists in the ceiling. From this opening...I want to have a Fog or more preceisly...a volumetric light that comes down and into the scene. It should gradually fade as it get closer to the ground. I would like to have some noise in the light too as to simulate dust in the air. How do I do this and what are the best settings? Any help greatly appreciated. Cheers.