2d compositing and 3d compositing

Widely employed in film and video motion picture production, compositing is the combining of visual elements from separate sources into single images, often to create the illusion that all those elements are parts of the same scene. (For compositing in graphic design and still photography, see Photomontage.) Live-action shooting for compositing is variously called “blue screen,” “green screen,” “chroma key,” and other names. Today, most though not all compositing is achieved through digital image manipulation. Pre-digital compositing techniques, however, go back as far as the trick films of Georges Méliès in the late 19th century; and some are still in use.

All compositing involves the replacement of selected parts of an image with other material, usually, but not always, from another image. In the digital method of compositing, software commands designate a narrowly defined color as the part of an image to be replaced. Then every pixel within the designated range is replaced by the software with a pixel from another image, aligned to appear as part of the original. For example, a TV weather person is recorded in front of a plain blue or green screen, while compositing software replaces only the designated blue or green color with weather maps

Digital compositing is the process of digitally assembling multiple images to make a final image, typically for print, motion pictures or screen display. It is the evolution into the digital realm of optical film compositing.

Digital compositing systems
-Apple Shake
-Autodesk Combustion
-Autodesk Flint, Flame & Inferno
-Autodesk Smoke
-Autodesk Toxik
-Adobe After Effects
-Pinnacle Commotion
-eyeon Fusion
-D2 Nuke
-CompTime Industrial Light & Magic
-Industrial Light & Magic's proprietary Saber
-SideFX Houdini Halo (Houdini Master)
-Jahshaka