Optical motion capture: Theory and implementation

Abstract

Abstract: Motion capture is the process of recording real life movement of a subject as sequences of Cartesian coordinates in 3D space. Optical motion capture (OMC) uses cameras to reconstruct the body posture of the performer. One approach employs a set of multiple synchronized cameras to capture markers placed in strategic locations on the body. A motion capture system has applications in computer graphics for character animation, in virtual reality for human control-interface, and in video games for realistic simulation of human motion. In this tutorial, we discuss the theoretical and empirical aspects of an optical motion capture system. Basically, for a motion capture system implementation; the resources required consist of a number of synchronized cameras, an image acquisition system, a capturing area, and a special suit with markers. The locations of the markers on the suit are designed such that the required body parts (e.g. joints) are covered. We present our motion capture system using a framework that identifies different sub-problems to be solved in a modular way. The sub-problems involved in OMC are initialization, marker detection, spatial correspondence, temporal correspondence, and post-processing. In this tutorial, we discuss the theory involved in each sub-problem and the corresponding novel techniques used in the current implementation. The initialization includes setting up a human model and the computation of intrinsic and extrinsic camera calibration. Marker detection involves finding