When creating
computer-generated imagery
Computer-generated imagery (CGI) is the use of computer graphics to create or contribute to images in art, printed media, video games, simulators, and visual effects in films, television programs, shorts, commercials, and videos. The images may ...
, final scenes appearing in movies and television productions are usually produced by
rendering more than one "layer" or "pass," which are multiple images designed to be put together through digital
compositing
Compositing is the process or technique of combining visual elements from separate sources into single images, often to create the illusion that all those elements are parts of the same scene. Live-action shooting for compositing is variously ca ...
to form a completed frame.
Rendering in passes is based on a traditions in
motion control photography
Motion control photography is a technique used in Photograph, still and motion photography that enables precise control of, and optionally also allows repetition of, camera movements. It can be used to facilitate special effects photography. Th ...
which predate CGI. As an example, for a visual effects shot, a camera could be programmed to move past a physical model of a spaceship in one pass to film the fully lit beauty pass of the ship, and then to repeat exactly the same camera move passing the ship again to photograph additional elements such as the illuminated windows in the ship or its thrusters. Once all of the passes were filmed, they could then be optically printed together to form a completed shot.
The terms ''render layers'' and ''render passes'' are sometimes used interchangeably. However, rendering in layers refers specifically to separating different ''objects'' into separate images, such as a layer each for foreground characters, sets, distant landscape, and sky. On the other hand, rendering in passes refers to separating out different ''aspects'' of the scene, such as shadows, highlights, or reflections, into separate images.
References
{{DEFAULTSORT:Render Layers
Computer graphics