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Generating optimized marker-based rigid bodies for optical tracking systems

Marker-based optical tracking systems are often used to track objects that are equipped with a certain number of passive or active point markers. Fixed configurations of these markers, so-called rigid bodies, can be detected by, for example, infrared stereo-based camera systems, and their position and orientation can be reconstructed by corresponding tracking algorithms. The main issue in designing the geometrical constellation of these markers and their 3D positions is to allow robust identification and tracking of multiple objects, and this design process is considered to be an essential and challenging task. At present, the design process is based on trial-and-error: the designer constructs a marker configuration, evaluates it in a given setup, and rearranges the marker positions within the configuration if necessary. Even though single ready-made rigid bodies permit sufficiently good tracking, it is not ensured that the corresponding arrangements of markers meet any quality criteria in terms of reliability and robustness. Furthermore, it is unclear whether it is possible to add further rigid bodies to the setup which are sufficiently distinguishable from the given ones. In this paper, we present an approach to semi-automatically generate marker-based rigid bodies which are optimal with respect to the properties of the tracking system for which they are used, e.g., granularity, accuracy, or jitter. Our procedure which is aimed at supporting the design process as well as improving tracking generates configurations for several devices associated with an arbitrary set of point-based markers. We discuss both the technical background of our approach and the results of an evaluation comparing the tracking quality of commercially available devices to the rigid bodies generated by our approach.