Animation is a difficult art. From its inception, animators have tried to show actions that normally are never seen in slow motion. For example, Is your back straight or bent when sprinting? What does your non-shooting arm do when you fire a pistol? How exactly does someone look falling down a flight of stairs?
When animated films (cartoons) were first made - hand-drawn, cell by cell, the artists would study frames of film, to analyse how something moved. "Something" can be animals or humans - particularly humans running, crouching, turning around quickly, firing a gun - all actions that, while happening all the time, can be difficult to break down to their elements.
When animated film was moved from the cellulose cells of the drawing boards to the computers - with pioneers such as Pixar and their Toy Story leading the way, new techniques were devised to control movement of a character - Motion capture being one of them.
While not being used too often in "normal" animated films, motion capture is increasingly important in movies where the animated characters play alongside real actors. Obviously, for the sake of realism, you cannot have animated characters defy the laws of physics - something that is possible, but difficult to do without the use of motion capture.
How Motion Capture Works
Motion capture works by dressing an actor in a single-coloured coverall, usually black. This coverall has dots on it that sensors can measure. Some systems use light and reflective dots, others use magnetic fields, but the principle is all the same:
Imagine a suit where all the key body parts have been marked with a bright white dot. The feet, knees, hips, stomach, back, shoulders, elbows, hands, neck, head and face are all marked. Now, when the actor moves in front of the system, the relative points are recorded into a computer. When the points then are connected to the "joints" in the animated character, and the movements of the actor are used as a guide to animating the character, this results in a particularly lifelike animation.
Characters like Lord of the Rings' Gollum and Shrek's princess gain their realistic characteristics through the use of motion capture. Video game companies are also increasingly using the technology to make their game characters more realistic.
Motion capture is not only used in the entertainment industry. Top athletes use it as well, to analyse their motoric development in training sessions, and to be able to perfect whatever sports they are doing. People doing high jumping and fencing have been known to use motion capture, as their movements are particularly precise, yet too fast to analyse using conventional methods.
There are many companies that offer motion capture services. A Google
search for "motion capture" should put you well on your way.