Abstract

This article describes OpenTracker, an open software architecture that provides a framework for the di#erent tasks involved in tracking input devices and processing multimodal input data in virtual environments and augmented reality application. The OpenTracker framework eases the development and maintenance of hardware setups in a more flexible manner than what is typically o#ered by virtual reality development packages. This goal is achieved by using an object-oriented design based on XML, taking full advantage of this new technology by allowing to use standard XML tools for development, configuration and documentation. The OpenTracker engine is based on a data flow concept for multimodal events. A multi-threaded execution model takes care of tunable performance. Transparent network access allows easy development of decoupled simulation models. Finally, the application developer's interface features both a time-based and an event based model, that can be used simultaneously, to serve a large range of applications. OpenTracker is a first attempt towards a "write once, input anywhere" approach to virtual reality application development. To support these claims, integration into an existing augmented reality system is demonstrated. We also show how a prototype tracking equipment for mobile augmented reality can be assembled from Preprint submitted to Elsevier Science 12 April 2001 consumer input devices with the aid of OpenTracker. Once development is su#- ciently mature, it is planned to make Open-Tracker available to the public under an open source software license. Key words: Tracking, Mobile Augmented Reality, Virtual Reality, XML 1

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