In this paper, we present a Fitts' law-based formal evaluation process and the corresponding results for 3D object manipulation techniques based on a virtual hand metaphor in a tangible augmented reality (TAR) environment. Specifically, we extend the design parameters of the 1D scale Fitts' law to 3D scale and then refine an evaluation model in order to bring generality and ease of adaptation to various TAR applications. Next, we implement and compare standard TAR manipulation techniques using a cup, a paddle, a cube, and a proposed extended paddle prop. Most manipulation techniques were well-modeled in terms of linear regression according to Fitts' law, with a correlation coefficient value of over 0.9. Notably, the throughput by ISO 9241-9 of the extended paddle technique peaked at around 1.39 to 2 times higher than in the other techniques, due to the instant 3D positioning of the 3D objects. In the discussion, we subsequently examine the characteristics of the TAR manipulation techniques in terms of stability, speed, comfort, and understanding. As a result, our evaluation process, results, and analysis can be useful in guiding the design and implementation of future TAR interfaces.
Taejin Ha, Woontack Woo, "An Empirical Evaluation of Virtual Hand Techniques for 3D Object Manipulation in a Tangible Augmented Reality Environment," IEEE 3D User Interfaces, pp. 91-98, 2010.