Or they have connected the 360 to the computer (like how mine is right now), go to power cinema, press record, and stop the recording when you want to. Then you go to something else, take photos, open it in PS (or maybe GIMP) and render it.
These are game photos:



Well, the last one i put in the same category, 'cause it took me a hell of a long time to get the pieces together and i put so many rendered photos in there.
"...You might think I'm losing my mind, but I will shy away from the specifics..."
gamertag: path090