whether person-specific training or other human assistance is required real-time performance (which is only possible if no training or supervision is required) whether they need an additional source of information such as projected patterns or invisible paint such as used in the Mova system. To date, no system is ideal with respect to all these criteria. For example, the Neven Vision system was fully automatic and required no hidden patterns or per-person training, but was 2D. The Face/Off system is 3D, automatic, and real-time but requires projected patterns. Facial expression capture Technology Digital video-based methods are becoming increasingly preferred, as mechanical systems tend to be cumbersome and difficult to use. Using digital cameras, the input user's expressions are processed to provide the head pose, which allows the software to then find the eyes, nose and mouth. The face is initially calibrated using a neutral expression. Then depending on the architecture, the eyebrows, eyelids, cheeks, and mouth can be processed as differences from the neutral expression. This is done by looking for the edges of the lips for instance and recognizing it as a unique object. Often contrast enhancing makeup or markers are worn, or some other method to make the processing faster. Like voice recognition, the best techniques are only good 90 percent of the time, requiring a great deal of tweaking by hand, or tolerance for errors. Since computer generated characters don't actually have muscles, different techniques are used to achieve the same results. Some animators create bones or objects that are controlled by the capture software, and move them accordingly, which when the character is rigged correctly gives a good approximation. Since faces are very elastic this technique is often mixed with others, adjusting the weights differently for the skin elasticity and other factors depending on the desired expressions. Usage Several commercial companies are developing products that have been used, but are rather expensive. It is expected that this will become a major input device for computer games once the software is available in an affordable format, but the hardware and software do not yet exist, despite the research for the last 15 years producing results that are almost usable. See also Eye tracking Computer facial animation Facial recognition system Facial Action Coding System Deepfake References External links Carnegie Mellon University Delft University of Technology Intel Sheffield and Otago Computer animation Facial expressions Computing input devices Motion capture