BraTrack

BraTrack: A Low-Cost Marker-based Optical Stereo Tracking System Francisco Pinto1

Alexandre Buaes2

Diego Francio3

Alécio Binotto4

Pedro Santos5

PPGC UFRGS, MAMS Tecnologia,

MAMS Tecnologia

MAMS Tecnologia, CETA/SENAI-RS

PPGC UFRGS, Fraunhofer IGD

Fraunhofer IGD

CETA/SENAI-RS 1 INTRODUCTION Optical motion tracking systems are widely employed in virtualand mixed reality applications enabling users to directly interact with 3D space. Important efforts have been made to make such technologies available to a larger group of users by significantly reducing their deployment costs. In this poster we introduce the result of a German-Brazilian cooperation: The first commercial low-cost marker-based optical tracking system developed in South-America. Despite using cheaper technologies and being low-cost which usually imply worse performance and accuracy, we developed a system with sufficient accuracy for professional use.

efficient infrared LEDs. Image acquisition by all camera modules is synchronized by a software module. A 2D pre-processing identifies visible markers in each camera. A 3D reconstruction module finds co-related markers visible in more than one camera and identifies calibrated artifacts using epipolar geometry. Each artifact is tracked and identified with an ID, position and orientation. Integrating BraTrack with VR and AR applications is a simple task and the system comprises simple tools for calibration and artifact management.

There have been significant research efforts to develop cheaper tracking devices to provide interaction capabilities in virutal- and mixed reality. The Augmented Reality Tool Kit (ARToolkit) [1] is a good example of a very popular low-cost academic optical tracker working with any type of webcam. As a non-academic example of affordable tracking systems, Nintendo's latest video game console (Nintendo Wii) comes with the Wiimote interaction device containing a built-in motion tracker that allows for immersive interaction metaphors in home environments. However, most such available low-cost solutions lack in suitability for professional applications due to their usually insufficient accuracy, tracking range or latency time. The starting point of this project was PTrack [2], an academic marker-based single-camera tracker developed at Fraunhofer IGD. PTrack development has shown that an accurate optical tracking system can be built from components that are affordable for a much wider group of users, from the academic AR/VR community to companies’ developers. The performance and accuracy of PTrack were assessed through a comprehensive set of experiments which have proved the suitability of the system for professional applications. One of the main topics raised by PTrack as further research was an extension of the system into a multiple stereo camera configuration, which led to the present work. 2 EXPOSITION BraTrack (Fig. 1) has a modular architecture where each task is performed by a specific software or hardware component.

Figure 2: BraTrack Technical Specification

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CONCLUSION To our knowledge BraTrack is the first commercial low-cost marker-based optical tracking system developed in SouthAmerica making this technology available to communities which have until now been deprived from such technologies due to their high cost without compromising on accuracy, tracking range or latency (Fig. 2). ACKNOWLEDGEMENTS This project is being developed in a team composed by MAMS Tecnologia, CETA (Center of Excellence in Advanced Technologies, SENAI-RS) and Fraunhofer IGD in partnership with Absolut Technologies, having Petrobras as first customer. We also thank FINEP (Brazilian Research and Projects Financing) for supporting funds to this research. REFERENCES

Figure 1: BraTrack Basic System

The camera modules are hardware components consisting of offthe-shelf USB cameras and custom-made electronic boards to provide flash strobes, which use an expressive number of highly

Copyright is held by the author / owner(s). SIGGRAPH 2008, Los Angeles, California, August 11–15, 2008. ISBN 978-1-60558-466-9/08/0008

[1]

KATO, H.; BILLINGHURST, M. Marker Tracking and HMD Calibration for a Video-based Augmented Reality Conferencing System. In: IEEE AND ACM INTERNATIONAL WORKSHOP ON AUGMENTED REALITY, 2., San Francisco, USA, Oct. 1999. Proceedings… San Francisco, 1999. p. 85-94.

[2]

SANTOS, P. et al. PTrack: Introducing a Novel Iterative Geometric Pose Estimation for a Marker-based Single Camera Tracking System. In: IEEE VIRTUAL REALITY CONFERENCE, Alexandria, USA, Mar. 2006. Proceedings… Alexandria, USA, 2006. p. 143-150.