Motion Capture

Motion capture or mocap is the process of recording the movement of objects or people. It is used in military, entertainment, sports, and medical applications, and for validation of computer vision and robotics. In filmmaking and video game development, it refers to recording actions of human actors, and using that information to animate digital character models in 2D or 3D computer animation. When it includes face and fingers or captures subtle expressions, it is often referred to as performance capture. In many fields, motion capture is sometimes called motion tracking, but in filmmaking and games, motion tracking more usually refers to match moving.

In motion capture sessions, movements of one or more actors are sampled many times per second, early techniques used images from multiple cameras and calculate 3D positions, motion capture often records only the movements of the actor, not his or her visual appearance. This animation data is often mapped to a 3D model so that the model performs the same actions as the actor. This process may be contrasted to the older technique of rotoscope, such as the Ralph Bakshi 1978 The Lord of the Rings and 1981 American Pop animated films where the motion of an actor was filmed, then the film used as a guide for the frame-by-frame motion of a hand-drawn animated character.

Camera movements can also be motion captured so that a virtual camera in the scene will pan, tilt, or dolly around the stage driven by a camera operator while the actor is performing, and the motion capture system can capture the camera and props as well as the actor's performance. This allows the computer-generated characters, images and sets to have the same perspective as the video images from the camera. A computer processes the data and displays the movements of the actor, providing the desired camera positions in terms of objects in the set. Retroactively obtaining camera movement data from the captured footage is known as match moving or camera tracking.