Redirected Touching

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

Augmentation Algorithms for Survivable Network Topologies in Wired and Optical Networks

Abstract — This paper falls in the area of survivable topology design where the goal is to design robust network topologies that anticipate link or node failures. While some survivable networks are designed from scratch, others must be built by augmenting existing networks with sufficient resources to enable survivability. The general topology augmentation problem addresses the general question: what additional resources are required to build upon an existing network to enhance its survivability? A typical such problem involves finding the fewest links to add to a topology to make the topology 2-edge-connected. This paper considers a costconstrained variation of that problem: given a topology, a set of potential links each with a cost, and a limited budget, find links that can be added to enhance the topology’s biconnectivity. We also consider an extension to optical networks in which fiber and wavelength resources are part of the problem. We present several different heuristics for both general wired networks and for optical networks. The main result of this work is that no single heuristic alone is effective but that a combination of them find near-optimal solutions when compared with simulated annealing. Index Terms — Survivable network design, reliability, graph augmentation, topology desig

Effective cooperative haptic interaction over the Internet

We present a system that enables, for the first time, effective transatlantic cooperative haptic manipulation of objects whose motion is computed using a physically-based model. We propose a technique for maintaining synchrony between simulations in a peer-to-peer system, while providing responsive direct manipulation for all users. The effectiveness of this approach is determined through extensive user trials involving concurrent haptic manipulation of a shared object. A CAD assembly task, using physically-based motion simulation and haptic feedback, was carried out between the USA and the UK with network latencies in the order of 120ms. We compare the effects of latency on synchrony between peers over the Internet with a low latency (0.5ms) local area network. Both quantitatively and qualitatively, when using our technique, the performance achieved over the Internet is comparable to that on a LAN. As such, this technique constitutes a significant step forward for distributed haptic collaboration