CGI Compositing

By far the most common application of digital compositing is to composite CGI.
Whether it is for a $100,000 commercial or for a $100 million dollar movie, the
CGI is created in a computer and composited over some kind of a background image.
The background image is very often live action, meaning it was shot on fi lm or video,
but it too could be CGI that was also created in a computer, or it may be a digital
matte painting. Regardless of where the background came from, the digital compositor
puts it all together and gives it the fi nal touch of photorealism. Figure illustrates

a basic CGI composite where the jet fighter was created in the computer, the
background is live action footage, and the fi nal composite puts the jet fi ghter into
the background.

Today, CGI goes far beyond jet fighters and dinosaurs. Recent advances in the
technology have made it possible to create a very wide range of incredibly realistic
synthetic objects for compositing. Beyond the obvious things such as cars, airplanes,
and rampaging beasts, CGI has mastered the ability to create photorealistic hair, skin,
cloth, clouds, fog, fi re, and even water. It has even become common practice to use
a “digital double” when you want the movie star to execute a daring stunt that is
beyond even the expert stunt double. It will not be long before the fi rst “cyber thespian”
(an all CGI character) stars in what would otherwise be a live action movie.
However, after all the spaceships, beasts, water, and fi re have been rendered, somebody
has to composite them all together. That somebody is the dauntless digital
compositor.