G6-1　Analysis of movement and performance of pointing in real and stereoscopic environments

Abstract

Effective interactions in virtual environment require acceptable level of movement quality to induce presence to its users. This study investigates the movement performances in projection based large stereoscopic displays. Fifteen self-declared right-handed individuals with normal or corrected to normal visual acuity participated in the experiment that compared the performances in stereoscopic and real environments. Participants viewed virtual objects displayed at a combination of three different parallax and nine frontal plane positions and then reached the perceived position of the targets with a direct pointing technique by holding a stick. An Optitrack system, composed six infrared cameras, used to track reflective markers attached to tips of the pointing sticks. The three-dimensional data, collected by the motion system at a rate of 120 frames per second, was used to compute the kinematics -movement time, throughput, peak velocity of reaching real/virtual objects. The velocity profile was also evaluated in order to compare the movement behaviors depicted in the stereoscopic displays with respect to that in the physical world. The result indicated that the movement in the projection based stereoscopic display was slower and needed longer confirmation time as compared to the real world equivalent. This might be because of the difficulty and inaccurate perception of distance associated with a stereoscopic viewing, as reported by a number of previous studies. However, the velocity profile did not show a significant difference between the real and stereoscopic conditions, where the trajectory was dominated by a primary movement phase with only one peak velocity. The comparable kinematics and movement behaviors in stereoscopic displays encourage the use of direct pointing that would enhance reaching and grasping tasks -which are important in applications such as rehabilitation, surgical training, and other programs that use upper limbs. In addition, the more natural interaction in pointing minimizes the effort of learning new skills to use other devices.