GRADES 9-12
MOTION CAPTURE AND ANALYSIS

BACKGROUND INFORMATION: Motion Capture There are many ways to capture information in scientific studies. An entire industry exists dedicated to instrumentation (collection of information with scientific equipment and instruments). A variety of equipment exists to calibrate (test and determine accuracy), accumulate and analyze motion data. In sports, equipment such as in-sole sensors or force plates measure the pressure that the athlete imposes on the ground as he or she performs. It's not surprising that equipment used to measure the gaits and motions of the most elite athletes are also used in the medical and rehabilitative fields to analyze the motions of individuals with limited and restrictive movements. The same equipment monitors and looks for improvements as the person recovers from an injury. There are four major methods of motion capture: optical, magnetic, electromagnetic (magnetism created through an electric current), and "non-invasive" video systems. Motion capture techniques are not only used to study athletes, but used in animated films and video games. Today, computer animated characters can look very realistic. How do they do that? One technique uses small reflective balls. The balls are attached to key joints and points on a person's body. Infra-red cameras are set up around the athlete or performer and can track the movement of these little balls. If one of the balls is out of view of the cameras, its position can be determined by the other cameras. This is called an "optical" system and is typically limited to an indoor studio setting. Another technique uses magnetic sensors instead of balls. There are wires leading from these sensors into computer systems that collect the motion information. This is called a "magnetic" system and although the motion capture is not limited to a studio, the wires restrict very complicated motions. There are also methods that are "electromagnetic". These systems use body suits. These motions are collected by a computer and then used with animated or "synthetic" characters.