On the Right Track

  • Published 2000


he success of any virtual-reality experience depends on the user's sense of presence in the virtual environment. While believable graphics and familiar modes of interaction are important elements to achieving such presence, both are of little value if the user's navigation through the digital scene feels slow, stilted, or somehow out of sync, or if the user feels prohibitively constrained in space all effects of less-than-perfect motion tracking. A motion-tracking system is the hardware/software configuration through which a user's head position and orientation in a scene are communicated to the computer, which in turn adjusts the displayed image to reflect changes in the user's location. This is generally achieved through one of five types of motion-tracking technologies: mechanical, electromagnetic, inertial, optical, or acoustic. An ideal tracking system is one that is able to generate position and orientation computations in real time without compromising the graphical display or the user's freedom of motion. Unfortunately, such an ideal has yet to be realized. In reality, most tracking systems are forced to make techn o l o g y tradeoffs. Wi th mechanical tracking , fo r instance, the tracking hardware is physically attached to the object or person being tracked, so while such devices offer high accuracy, they restrict movement. Electromagnetic tracking measures the strength of the magnetic fields in coils attached to objects, which enables fast results, but the systems are prone to interference from metallic objects in the physical surr o u n d i n g s a n d they operate within a limited range. Inertial tracking systems, which operate by integrating voltages from gyros and accelerometers, suffer from drift and thus usually must be combined with another technology to be useful. In traditional optical systems, a fixedposition camera monitors the pulsations of light-emitting diodes (LEDs) attached to an object or user. As with magnetic systems, the response time is fast, but the systems are prone to line-ofsight problems and interference caused by ambient lighting. Finally, acoustic systems, which use ultrasound waves to measure position and orientation, are burdened by the slow speed of sound. As part of an ongoing effort to develop a system that avoids such tradeoffs, the Tracker Research Group at the University of North Carolina (http://www.cs.unc.edu/ ~tracker) has created a wide-area optoelectronic tracking technology that lets users move freely through full-scale virtual worlds in real time. Such a capability not only enables VR applications that would otherwise be difficult or impossible to achieve—such as the exploration of lifesize architectural designs and room-filling molecular models—but it is also expected to be of value to augmented reality (AR). In AR, real and digital worlds are superimposed into one scene through the use of see-through head-mounted displays that rely either on mirrors to represent the physical world or video input. Highly accurate motion tracking is crucial because even small tracking errors can result in unacceptable misregistration between real and virtual objects. On the Right Track A unique optical tracking system gives users greater freedom to explore virtual worlds

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@inproceedings{2000OnTR, title={On the Right Track}, author={}, year={2000} }