BACKGROUND - how?

hi, i’ve been wondering how to make a realistic background, that would look like room with no walls, no ending… You should see the horizont, but it should mix with flor very smooth… like for egzample in foto-studio or:

http://www.cgtalk.com/showthread.php?t=166277 - here

http://www.yeahthemovie.de/ - specially in here (CREEPS, or BOSS, or AMAZON movies)

i mean, not only to use GI or AO, but also a lamp making raytraced shadow.

ANY IDEAS ??

Add it as a texture to the World?

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