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Motion capture
Motion capture is the process of using the motions, actions and sometimes expressions of a human actor and animating a computer-rendered model from those actions to move a model exactly as the actor did. Further, camera movements and angles can be incorporated into the scene that are also used in the computer model. Motion capture is sometimes referred to as motion tracking, or mocap.
In a motion capture session, the actor will don special markers and complete their performance. Motion sensors may also be applied all over the face to capture expressions, and this information is called animation data. The animation data is then placed onto a 3D model. This is referred to as 3D motion capture, whereas 2D motion capture is something different entirely. Sometimes called rotoscoping, animators trace over live action to create 2D animation. One example of this technique is the recent film A Scanner Darkly.
Using Markers
There are two types of markers used on the actors during the motion capture process: active markers and passive markers. Passive markers merely reflect light to the camera, which doesn’t “see” anything else other than the reflected light. Active markers use LED lights with software instead. Newer technology that is currently emerging does not require markers of any sort, instead having software identify human forms and their actions.
Motion matching software
Match moving and motion capture go hand-in-hand. When a live scene is filmed with an ordinary camera and motion capture or other special effects are added, it must be incorporated seamlessly and with the same perspectives as any scenery or other objects. Two softwares that do this are Boujou and Mocha v2. Boujou allows for feature detection as well as terrain generation, which are applicable in adding special effects into scenes with little to no detail or markers, like a large body of water from a distance, or tracking very difficult terrain like leaf piles and meadows. Mocha v2 by Imagineer Systems is another tracking software that allows for the exporting of tracking data to editing software, and is used for tracking within an entire scene.
Tracking data and its uses
Some of the most notable uses of motion capture technology are Gollum The Lord of the Rings and Avatar, where the actors’ movements and expressions were captured extremely well and gave their characters life. Motion tracking data is also used in the creation of video games, as well as in medical applications to study human movements.