Advantages disadvantages and applications of motion capture
Advantages
Mo cap offers several advantages over traditional computer animation of a 3D model:
More rapid, sometimes even real time results can be obtained.
The amount of work does not vary with the complexity or length of the performance to the same degree when using traditional techniques.
Complex movement and realistic physical interactions such as secondary animation, weight and exchange of forces can be more easily recreated in a physically accurate manner.
Mocap technology allows one actor to play multiple roles within a single film.
Advantages over live action A movie that contains so large amounts of CGI that the actors would have to stay in front of a bluescreen and interact with invisible computer animated characters which is added later, trying to fit into a computer animated world, it is sometimes less problematic to make everything digital, including the actors. This way, all elements would fit together naturally and have the same visual look.
The director can choose any angle he desires from a scene, including angles that would have been hard or impossible in a live action movie.
Limitless possibilities for rotating effect.
Costumes, make-up, body size and age can be changed to whatever is needed.
There is no need to have light, colors and filters in mind when filming the motions, as this will be added digitally later.
Disadvantages
Specific hardware and special programs are required to obtain and process the data.
The cost of the software and equipment, personnel required can be prohibitive for small productions.
The capture system may have specific requirements for the space it is operated in.
When problems occur it is sometime 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.
Applying motion to quadruped characters can be difficult.
The technology can become obsolete every few years as better software and techniques are invented.
The 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 generally cannot be represented.
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 are generally not applicable.
If the computer model has different proportions from the capture subject artifacts may occur. For example, if a cartoon character has large, over-sized hands, these may intersect strangely with any other body part when the human actor brings them too close to his body.
The real life performance may not translate on to the computer model as expected.
Applications
Some video games use motion capture to animate athletes, martial artists, and other in-game characters.
Movies use motion capture for CG effects, in some cases replacing traditional cell animation, and for completely computer-generated creatures, such as Gollum, The Mummy, and King Kong.
In producing entire feature films with Computer animation, the industry is currently split between studios that use Motion Capture, and studios that do not. Out of the three nominees for the 2006 Academy Award for Best Animated Feature, two of the nominees ("Monster House" and the winner "Happy Feet") used Motion Capture, and only Pixar's Cars was animated without Motion Capture. In the ending credits of Pixar's latest film "Ratatouille," a stamp appears labelling the film as "100% Pure Animation -- No Motion Capture!" On the other hand, Pixar's parent The Walt Disney Company has announced that it will distribute Robert Zemeckis's "Christmas Carol" to be produced using "Performance Capture," the motion-capture approach that Zemeckis first used on "Polar Express."
Virtual Reality and Augmented Reality require real time input of the user's position and interaction with their environment, requiring more precision and speed than older motion capture systems could provide. Noise and errors from low resolution or low speed systems, and overly smoothed and filtered data with long latency contribute to "simulator sickness" where the lag and mismatch between visual and vestibular cues and computer generated images caused nausea and discomfort.
Gait analysis is the major application of motion capture in clinical medicine.
High speed-high resolution active marker systems can provide smooth data at low latency, allowing real time visualization in virtual and augmented reality systems. The remaining challenge that is almost possible with powerful graphic cards is mapping the images correctly to the real perspectives to prevent image mismatch.
Motion capture technology is frequently used in digital puppetry systems to aid in the performance of computer generated characters in real-time.
by
Antony
