Visual effects (vfx) is the term given to a sub-category of special effects in which images or film frames are created or manipulated for film and video. Visual effects usually involve the integration of live-action footage with computer generated imagery or other elements (such as pyrotechnics or model work) in order to create environments or scenarios which look realistic, but would be dangerous, costly, or simply impossible to capture on film. They have become increasingly common in big-budget films, and have also recently become accessible to the amateur filmmaker with the introduction of affordable animation and compositing software.
Visual effects are frequently integral to a movie's story and appeal. Although most visual-effects work is completed during post-production, it usually must be carefully planned and choreographed in pre-production and production.