CGI is Computer Generated Imagery.It is a development commonly used with films where by computer generated animations and images are added to film footage to enhance the film. CGI was first used in 1973 in a film called Westworld - a sci-fi film about robots and humans mixing which was directed by Michael Crichton.
This series of images shows the creation of one of the characters in Pirates Of The Carribean, where by CGI was heavily relied on.
CGI is usually used because computer generated imagery is a lot easier to control than other physical aspects such as in Walace and Gromit, where all the shots had individual plasticine models which were changed for each tiny movement. It is also used to create things that are not real, common in fantasy films.
Some films of the thriller genre that include CGI are Avatar, The Day After Tomorrow and The Butterfly Effect.
