Compositing, a technique used to superimpose footage onto other footage, is used extensively in movies from Star Wars to Titanic to Spider Man. Actors are filmed in front of a solid blue or green colored background (see figure 29-1).
In post-production, this background is eliminated and substituted with other footage (such as a miniature set or CGI rendering) with special software (see figure 29-2). The process is known by many names including blue screening, green screening, chroma-keying, and compositing. For simplicity, in the remainder of this chapter I’ll refer to this process as compositing.
Professional blue screens ...