Originally used as an analytical tool for biomechanics, motion capture technology, a.k.a. “mocap,” is now used in video game development, computer animation, sports training and troubleshooting, and clinical medicine. Movement is captured by placing sensors on or near each body joint. As joints move, the positions between sensors are recorded in software, which analyzes angles, velocities, accelerations, and impulses to create a digital movement map. Mocap technologies range from electromechanical and optical systems to those that use magnetic flux and inertial gyroscopes. The new IGS-190 system from Animazoo, Brighton, UK, uses 19 tiny inertial gyroscopes attached to an actor's body suit to record movements. A radio transmits this data to a receiver, where it is mapped to a skeleton that can be visualized in real-time.
For more information, visit animazoo.com.
Back story
The IGS-190 was the brainchild of Animazoo founder, Ali Kord, one of the cofounders of the original golf simulation game, Ingolf. With more than 16 years experience in the animation industry, Kord believed there was huge potential for the technology behind Ingolf. He was right. This technology became the basis for the animation tool now used worldwide for biomechanics and animation. When Kord surveyed the mocap market, he found many of the available products “unwieldy, expensive, and complicated,” so he set out to develop a better system.
Design dilemmas
In early iterations of the Animazoo system, Kord and his design team encountered issues with magnetic interference, as ferrous objects near the sensors were causing data output to be less than accurate. The team overcame this using software that ignores interference associated with the earth's magnetic field, instead tapping into the field's “dip angle and magnitude.” The zeroing process requires one cubic foot of space free of magnetic interference. A single inertial gyro takes a 30-second reading of the earth's magnetic dip angle and magnitude and feeds the information into a computer. Whenever the system's magnetometer encounters dip readings that don't match, it corrects the magnetic north readings accordingly.
Placing sensors on the body was also a bigger challenge than Kord had initially thought. The original concept was that special fasteners would be needed to hold sensors in position during operation. As it turned out, almost all of the sensor placement spots were on muscles, which do not stay static during limb movements. Kord and company then realized that all motion capture is inherently flawed, especially in optical systems that place reflective markers on joints, which move during limb motion, thus guaranteeing that all markers will move from their positions established at rest. The surprise was that gyros, unlike optical markers, were better off not placed on joints, but rather on rigid limbs. The result? A more accurate system than optical methods, according to Kord.
Design impact
Animazoo's mocap technology is used by Rockstar North (producers of Grand Theft Auto), the BBC, RAI TV in Italy, and more than 50 universities including MIT. System prices start at $39,600.