Analysis of direct selection in head-mounted display environments

The design of 3D user interfaces (3DUIs) for immersive head-mounted display (HMD) environments is an inherently difficult task. The fact that usually haptic feedback is absent and that visual body feedback is missing, hinders an efficient direct interaction with virtual objects. Moreover, the perceptual conflicts, such as double vision and space misperception, as well as the well-known vergence-accommodation mismatch further complicate the interaction, in particular with virtual objects floating in the virtual environment (VE). However, the potential benefits of direct and natural interaction offered by immersive virtual environments (IVEs) encourage the research in the field to create more efficient selection methods. Utilizing a Fitts´ Law experiment, we analyzed the 3D direct selection of objects in the virtual 3D space as they might occur for 3D menus or floating objects in space. We examined the direct interaction space in front of the user and divided it into a set of interaction regions for which we compared different levels of selection difficulty. Our results indicate that the selection errors are highest along the view axis, less along the motion axis and marginal along the orthogonal plane. Based on these results we suggest some guidelines for the design of direct selection techniques in IVEs.