Modeling object pursuit for 3D interactive tasks in virtual reality

Models of interaction tasks are quantitative descriptions of relationships between human temporal performance and the spatial characteristics of the interactive tasks. Examples include Fitts´ law for modeling the pointing task and Accot and Zhai´s steering law for the path steering task, etc. Models can be used as guidelines to design efficient user interfaces and quantitatively evaluate interaction techniques and input devices. In this paper, we introduce a 3D object pursuit interaction task, in which users are required to continuously track a moving target in a virtual environment. The entire movement of the task is broken into a tracking phase and a correction phase. For each phase, we propose a model that has been verified by two experiments. As the experimental results show, the time for the tracking phase is fixed once a task has been established, while the time for the correction phase usually varies according to some characteristics of the task. It can be modeled as a function of path length, target width and the velocity with which the target moves. The proposed model can be used to quantitatively evaluate the efficiency of user interfaces that involve the interaction with moving objects.