Revisiting path steering for 3D manipulation tasks

The law of path steering, as proposed by Accot and Zhai, describes a quantitative relationship between human temporal performance and the path spatial characteristics. The steering law is formulated as a continuous goal crossing task, in which a large number of goals are crossed along the path. The steering law has been verified empirically for locomotion, in which a virtual driving task through straight and circular paths was performed. We revisit the path steering law for manipulation tasks in desktop virtual environments. We have conducted controlled experiments in which users operated a pen input device to steer a virtual ball through paths of varying length, width, curvature and orientation. Our results indicate that, although the steering law provides a good description of the overall task time as a function of index of difficulty ID=L/W, where L and W are the path length and width, it does not account for other relevant factors. We specifically show that the influence of curvature can be modeled by a percentage increase in steering time, independent of index of difficulty. The path orientation relative to the viewing direction has a periodic effect on the steering time, which can be optimally described by a function of Fourier series expansions. In addition, there is also an effect of the handedness of the subjects on the steering between the left and right districts in 3D manipulation tasks.