Creating atmosphere without fog volumes?

Hi.

Edit : ok its been long day i completely misread your post.
I need to go read and research on this masking out areas thing.

If you know the document that refers to this please point me there. Or if you would be so kind to give a brief explanation of what im researching.
I know what masking is, but how i would go about masking something… perhaps something similar to a world based location, like the example they used to make things transparent around the player… i can use that i guess… then just add sphere or other things where i want the masking to occur… hmmm.

Am i on the right track?
Thx man… sorry had too much coffee