In the early days of cinema, special effects were produced as the cameras rolled to create what are called "in-camera effects." To create characters and locations that don't really exist, filmmakers would turn to such tools as stop-motion animation, miniatures and matte paintings, often compositing two images to create the effect of actors and special effects interacting.
The first major instance of CGI occurred with the science fiction film "Westworld" (1973), which used two-dimensional computer graphics to create shots seen from the point of view of a robot killer. The 1976 sequel, "Futureworld," also proved notable for featuring the first instance of fully three-dimensional computer animation to create a computerized rendering of the actor Peter Fonda. Other sci-fi films in the 1970s like "Star Wars" and "Alien" would use CGI to render futuristic computer screens, while "Superman" used the technology to create its eye-catching title sequence.
Soon movies would use CGI to create more than just computer screens. Films like "Star Trek II: The Wrath of Khan" (1982) used CGI to create entire fantastical sequences, "The Last Starfighter" (1984) integrated CGI effects with live-action footage and "Tron" (1982) used CGI to create the computer world that the characters enter. This effect has carried on to films like "Sky Captain and the World of Tomorrow" (2004), "Sin City" (2005) and "300" (2006), which film their actors in front of blue or green screens while adding backgrounds and visual effects later, creating entirely computer-generated worlds within the films.
As CGI technology improved, filmmakers became able to create entire characters in films. For example, the film "Young Sherlock Holmes" became the first film to use an entirely CGI character in the form of a supernatural knight. Previously a film might have relied on puppetry and stuntmen in suits to create a fantastic character like that. Also notable for popularizing CG characters is "Terminator 2: Judgment Day," which integrates a CGI character with actors to create a robot made of "liquid metal" that's capable of transforming into human forms. Similarly, CGI characters can be used in the place of stuntmen for certain special effects sequences.
As CGI became increasingly popular, producers of animated films began turning to the technology. While short films from Pixar like "Luxo Jr" (1986) and "Tin Toy" (1988) showed off the capabilities of CG animation, major films like Disney's "Beauty and the Beast" (1991) incorporated computer animation with its traditional cel animation. As full-length films like "Toy Story" (1995) started to appear, fully computer-animated films became more frequent.