Evaluating Direct Pointing and Indirect Cursor Interactions with Fitts' Law in Stereoscopic Environments

The development of virtual environment research has reached the stage of human interaction with three-dimensional (3D) objects. In this study, Fitts' method was used for such interaction in a virtual environment, and the applicability of Fitts' law in 3D virtual environments was also considered. An experiment was using two modes of interaction (direct interaction and indirect interaction) that utilize different techniques depending on how users interact with a 3D object. Both interaction techniques were applied with three indexes of difficulty and three egocentric target distances (distance from the user to the target). Movement time and throughput were measured for each interaction technique. The results showed that the direct pointing technique is more efficient for interaction with targets close to the user, while the indirect cursor technique may be a viable option for targets further away from the user. The throughput was found to be significantly higher for the direct pointing technique compared to the indirect cursor technique. The results of mean movement time were highly correlated with the targets' index of difficulty for all interaction techniques, which is supporting evidence that Fitts' law can be applied to interactions in 3D virtual environments. Based on the results, developers of VE applications may relate to these findings in designing proper user interactions.