Andy Serkis in his motion capture bodysuit, on the set of King Kong (2005).
Motion capture (Mo-cap for short) is the process of recording the movement of objects or people. It is used in military,entertainment, sports, 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 charactermodels 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 usually refers more to match moving.
Advantages and Disadvantages[]
Advantages[]
- More rapid, even real time results can be obtained. In entertainment applications this can reduce the costs of keyframe-based animation. The Hand Over technique is an example of this.
- The amount of work does not vary with the complexity or length of the performance to the same degree as when using traditional techniques. This allows many tests to be done with different styles or deliveries, giving a different personality only limited by the talent of the actor.
- Complex movement and realistic physical interactions such as secondary motions, weight and exchange of forces can be easily recreated in a physically accurate manner.
- The amount of animation data that can be produced within a given time is extremely large when compared to traditional animation techniques. This contributes to both cost effectiveness and meeting production deadlines.
- Potential for free software and third party solutions reducing its costs.
Disadvantages[]
- Specific hardware and special software programs are required to obtain and process the data.
- The cost of the software, equipment and personnel required can be prohibitive for small productions.
- The capture system may have specific requirements for the space it is operated in, depending on camera field of view or magnetic distortion.
- When problems occur, it is easier to reshoot the scene rather than trying to manipulate the data. Only a few systems allow real time viewing of the data to decide if the take needs to be redone.
- The initial results are limited to what can be performed within the capture volume without extra editing of the data.
- Movement that does not follow the laws of physics cannot be captured.
- Traditional animation techniques, such as added emphasis on anticipation and follow through, secondary motion or manipulating the shape of the character, as with squash and stretch animation techniques, must be added later.
- If the computer model has different proportions from the capture subject, artefacts may occur. For example, if a cartoon character has large, over-sized hands, these may intersect the character's body if the human performer is not careful with their physical motion.