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.
“The insidiousness of science lies in its claim to be not a subject, but a method.”
“Guys ask me, don't I get burned out? How can you get burned out doing something you love? I ask you, have you ever got tired of kissing a pretty girl?”