Luv Kohli

Redirected touching: Warping space to remap passive haptics

There is an increasing interest in deployable virtual military training systems. Haptic feedback for these training systems can enable users to interact more naturally with the training environment, but is difficult to deploy. Passive haptic feedback is very compelling, but it is also inflexible. Changes made to virtual objects can require time-consuming changes to their physical passive-haptic counterparts. This poster explores the possibility of mapping many differently shaped virtual objects onto one physical object by warping virtual space and exploiting the dominance of the visual system. A first implementation that maps different virtual objects onto dynamically captured physical geometry is presented, and potential applications to deployable military trainers are discussed.

Taxonomy and Implementation of Redirection Techniques for Ubiquitous Passive Haptic Feedback

Traveling through immersive virtual environments (IVEs) by means of real walking is an important activity to increase naturalness of VR-based interaction. However, the size of the virtual world often exceeds the size of the tracked space so that a straightforward implementation of omni-directional and unlimited walking is not possible. Redirected walking is one concept to solve this problem of walking in IVEs by inconspicuously guiding the user on a physical path that may differ from the path the user visually perceives. When the user approaches a virtual object she can be redirected to a real proxy object that is registered to the virtual counterpart and provides passive haptic feedback. In such passive haptic environments, any number of virtual objects can be mapped to proxy objects having similar haptic properties, e.g., size, shape and texture. The user can sense a virtual object by touching its real world counterpart. Redirecting a user to a registered proxy object makes it necessary to predict the users intended position in the IVE. Based on this target position we determine a path through the physical space such that the user is guided to the registered proxy object. We present a taxonomy of possible redirection techniques that enable user guidance such that inconsistencies between visual and proprioceptive stimuli are imperceptible. We describe how a users target in the virtual world can be predicted reliably and how a corresponding real-world path to the registered proxy object can be derived.

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

Redirected Touching: Training and adaptation in warped virtual spaces

Redirected Touching is a technique in which virtual space is warped to map many virtual objects onto one real object that serves as a passive haptic prop. Recent work suggests that this mapping can often be predictably unnoticeable and have little effect on task performance. We investigated training and adaptation on a rapid aiming task in a real environment, an unwarped virtual environment, and a warped virtual environment. Participants who experienced a warped virtual space reported an initial strange sensation, but adapted to the warped space after short repeated exposure. Our data indicate that all the virtual training was less effective than real-world training, but after adaptation, participants trained as well in a warped virtual space as in an unwarped one.

Towards Effective Information Display Using Vibrotactile Apparent Motion

In this paper, we explore the use of tactile apparent motion at different speeds for information display. A prototype vibrotactile tactor array was constructed, consisting of three rings of five voice-coil tactors each, and mounted on the upper arm of test subjects. The results of two experiments are presented: a study on the sensitivity to differences in apparent motion speed, and a study on users’ ability to differentiate four motion patterns at three different speeds. Users had little trouble with pattern identification, but found absolute speed recognition difficult. Several ideas for future exploration of tactile apparent motion for general-purpose information displays are presented.

Warping virtual space for low-cost haptic feedback

With the introduction of the Nintendo Wii, Playstation Move, and Microsoft Kinect, gaming and virtual reality technologies have begun to merge. These technologies have enabled low-cost, more-natural interaction with games and virtual environments (VEs). However, the sense of touch is usually missing. Interacting with virtual objects often means holding a hand in the air, which can be tiring if done for long. I present a technique to turn simple objects into haptic surfaces for virtual objects, extending earlier work on Redirected Touching [Kohli et al. 2012].

Latency Compensation by Horizontal Scanline Selection for Head-Mounted Displays

A fundamental task of a virtual-environment system is to present images that change appropriately as the users head moves. Latency produces registration error causing the scene to appear spatially unstable. To improve the spatial stability of the scene, we built a system that, immediately before scanout to a head-mounted raster display, selects a portion of each scanline from an image rendered at a wider display width. The pixel selection corrects for yaw head rotations and effectively reduces latency for yaw to the millisecond range. In informal evaluations, users consistently judged visual scenes more stable and reported no additional visual artifacts with horizontal scanline selection than the same system without. Scanline-selection hardware can be added to existing virtual-reality systems as an external device between the graphics card and the raster display.

Experiments in Mixed Reality

As part of the Institute for Creative Technologies and the School of Cinematic Arts at the University of Southern California, the Mixed Reality lab develops technologies and techniques for presenting realistic immersive training experiences. Such experiences typically place users within a complex ecology of social actors, physical objects, and collections of intents, motivations, relationships, and other psychological constructs. Currently, it remains infeasible to completely synthesize the interactivity and sensory signatures of such ecologies. For this reason, the lab advocates mixed reality methods for training and conducts experiments exploring such methods. Currently, the lab focuses on understanding and exploiting the elasticity of human perception with respect to representational differences between real and virtual environments. This paper presents an overview of three projects: techniques for redirected walking, displays for the representation of virtual humans, and audio processing to increase stress.