CGI is done after the film is done. It's through the computer. Most of the film is not computer-generated special effects. Most of it is that creature that is in the room with you.
“A work-room should be like an old shoe; no matter how shabby, it's better than a new one.”
“The buildings that I build very often have a dreamlike reality. I don't mean by that they have a fantasy quality at all, in fact quite the reverse. They contain in some degree the ingredients that give dreams their power... stuff that's very close to us.”