Computer-generated imagery (CGI) is defined as graphics generated by a computer and used as special effects in movies

Cinema has always relied on special effects to make the impossible seem possible to viewers. Over the years, the tools filmmakers use have evolved from actual physical objects to relying on computers to create special effects for films. Elements created for films via computers are called computer-generated images (CGI).
Precursors
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.
Early CGI
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 i ...more