With The Hobbit: The Desolation of Smaug now in theatres, Joe Letteri, the Oscar-winning co-creator of Gollum on screen, writes for the journal Nature about the evolution of computer animation. “Computer animation is a natural extension of hand-drawn methods developed during the early-twentieth-century golden age of ‘cel’ animation ushered in by Walt Disney, in which a series of images is played back at speed to give the illusion of life. Just as we do today, animators used a variety of reference techniques to capture the essence of organic movement. Snow White’s dance with the dwarves in Disney’s 1937 film was created by matching the movements of a live, filmed dancer, using a technique called rotoscoping — in the most basic terms, tracing the motion from a film one frame at a time. This technique, although now slightly more sophisticated in its application, is still in use.”