Abstract

Motion capture is a technique which allows a computer system to track and record movements of real world objects for later uses, including character animation. Current high-end systems, costing in the $100,000's and up, are generally out of reach for many individuals' budgets. The MotionCreator system is an attempt to bring simple motion capture techniques to the typical user. I present a functional, 6 degree-of-freedom (DOF) input device, created using no more than a simple webcam and ping-pong balls.

The system consists of several distinct modules. Specifically, the input device consisted of three differently-coloured ping-pong balls rigidly attached together and manipulated by the user. The motion of this device is captured in real-time video. Image processing techniques such as background abstraction, colour-histogram filtering, and converging meanshift algorithm were applied to track each ball independently. The three balls are thus corresponded to three points on the image plane. Using the fact that we know, a priori, the distance between the balls, we present an interactive inversion algorithm that lets us take advantage of this fact to compute the actual locations of the three balls in 3D coordinates. Thus, we obtain 6-DOF continuous input device using simple accessible hardware. We demonstrate the practicality of this by using it to drive an inverse kinematic animation control of a 2-link, 6-DOF structure.

"MotionCreator: An Accessible Optical Motion Capture System" by Colin Nickerson, Honors Thesis, Saint Mary's University, 82 pages, Adobe Acrobat (8,376 KB).