In immersive virtual environments, virtual objects cannot be touched. One solution is to use passive haptics - physical props to which virtual objects are registered. The result is compelling; when a user reaches out with a virtual hand to touch a virtual object, her real hand touches and feels a real object. However, for every virtual object to be touched, there must be an analogous physical prop. In the limit, an entire real-world infrastructure would need to be built and changed whenever a virtual scene is changed. Virtual objects and passive haptics have historically been mapped one-to-one. I demonstrate that the mapping need not be one-to-one. One can make a single passive real object provide useful haptic feedback for many virtual objects by exploiting human perception. I developed and investigated three categories of such techniques: 1. Move the virtual world to align different virtual objects in turn with the same real object 2. Move a virtual object into alignment with a real object 3. Map real hand motion to different virtual hand motion, e.g., when the real hand traces a real object, the virtual hand traces a differently shaped virtual object. The first two techniques were investigated for feasibility, and the third was explored more deeply. The first technique (Redirected Passive Haptics) enables users to touch multiple instances of a virtual object, with haptic feedback provided by a single real object. The second technique (The Haptic Hand) attaches a larger-than-hand virtual user interface to the non-dominant hand, mapping the currently relevant part of the interface onto the palm. The third technique (Redirected Touching) warps virtual space to map many differently shaped virtual objects onto a single real object, introducing a discrepancy between real and virtual hand motions. Two studies investigated the technique's effect on task performance and its potential for use in aircraft cockpit procedures training. Users adapt rather quickly to real-virtual discrepancy, and after adaptation, users perform no worse with discrepant virtual objects than with one-to-one virtual objects. Redirected Touching shows promise for training and entertainment applications.Doctor of Philosoph
