The Force Arrows disappear for non support-phase frames, since no ground contact forces are applied then. We have found that at the end of the flight phase, the foot strikes the ground with a significant forward force. Then, as the foot stabilizes and prepares for lift-off, the ForceArrow changes in length and rotation, intuitively showing the effects of the runner's shifting weight. Joint Trajectory Tracers Joint Trajectory Tracers graph the path of a joint across time. Here, the runner's right elbow follows a periodic path with low amplitude.
Tracers plot the movement of a joint over time.
Every given number of frames, a Tracer appears in the Java3D universe, marking the location of the joint at that frame. Tracers emphasize the periodicity of a motion, as well as highlight any differences between cycles. Tracers also enhance motion comparisons, displaying, for example, that at a particular frame, Runner A's elbow is much higher than Runner B's elbow. Horizontal lines to emphasize stride length Related Reading Information Design Braun, Marta. The Human Figure in Motion .