Robinson, M., Laurence, J., Hogue, A., Zacher, J. E., German, A., and Jenkin, M. IVY: Basic design and construction details, Proc ICAT 2002, Tokyo, Japan. Abstract Six-sided projective immersive displays present complex design and engineering constraints, especially if physical construction space is at a premium. Here we describe the physical construction of IVY (Immersive Visual environment at York), a six-sided projective immersive environment operating at York University, Toronto, Canada. IVY is a fully immersive (six-sided), projective, stereo visual environment that can be used for a range of tasks from space structure visualization to studying issues related to human perception in real and virtual environments.
Harris, L. and Jenkin, M. (Eds.), Levels of Perception, Springer Verlag, 2002. This book has been reviewed in Perception.
In this book the authors relate and discuss the idea that perceptual processes can be considered at many levels. A phenomenon that appears at one level may not be the same as a superficially similar phenomenon that appears at a different level. For example "induced motion" can be analyzed in terms of eye movements or at the retinal level or at a much higher cognitive level: how do these analyses fit together? The concept of levels also makes us think of the flow of information between levels, which leads to a consideration of the roles of top- down and bottom-up (or feed-forward, feed-back) flow. There are sections devoted to vestibular processing, eye movement processing and processing during brightness perception. The final section covers levels of processing in spatial vision. All scientists and graduate students working in vision will be interested in this book as well as people involved in using visual processes in computer animations, display design or the sensory systems of machines.
Kapralos, B., Jenkin, M. R. M., and Milios, E. Audio-visual localization of multiple speakers in a video teleconferencing setting. York University Technical Report CS-2002-02, 2002.
Attending to multiple speakers in a video teleconferencing setting is a complex task. From a visual point of view, multiple speakers can occur at different locations and present radically different appearances. From an audio point of view, multiple speakers may be speaking at the same time, and a background noise may make it difficult to localize sound sources without some a priori estimate of the sound source locations. This paper presents a novel sensor and corresponding sensing algorithms to address the task of attending simultansously to multiple speakers for video teleconferencing. A panoramic visual sensor is used to captuire a 360 degree view of the speakers in the environment, and from this view potential speakers are identified via a color histogram approach. A directional audio system based on beamforming is then used to confirm potential speakers and attend to them. Experimental evaluation of the sensor and its algorithms are presented including sample performance of the entire system in a teleconferencing setting.
Dudek, G., Jenkin, M., and Milios, E., A taxonomy of multirobot systems. In Robot Teams: From Diversity to Polymorphism, T. Balch and L. E. Parker (Eds.), 2002.
A key difficulty in the design of multi-agent robotic systems is the size and complexity of the space of possible designs. In order to make principled design decision, an understanding of the many possible system configurations is essential. In Dudek et al. [DJMW96] we presented a taxonomoy that classifies multi-agent systems according to communication, computational and other capabilities. In this chapter we update the taxonomoy developed in the early 1990's and place a number of recent multirobot systems within it.
Jaekl, P. M., Allison, R. S., Harris, L. R., Jasiobedzka, U. T., Jenkin, H. L., Jenkin, M. R., Zacher, J. E., and Zikovitz, D. C., Perceptual stability during head movement in virtual reality, Proc. IEEE VR 2002, Orlando, FL, 2002. Copyright IEEE.
Virtual reality displays introduce spatial distortions that are very hard to correct because of the difficulty of precisely modelling the camera from the nodal point of each eye. How significant are these distortions for spatial perception in virtual reality? In this study we used a helmet mounted display and a mechanical head tracker to investigate the tolerance to errors between head motions and the resulting visual display. The relationship between the head movement and the associated updating of the visual display was adjusted by subjects until the image was judged as stable relative to the world. Both rotational and translational movements were tested and the relationship between the movements and the direction of gravity was varied systematically. Typically, for the display to be judged as stable, subjects needed the visual world to be moved in the opposite direction of the head movement by an amount greater than the head movement itself, during both rotational and translational head movements, although a large range of movement was tolerated and judged as appearing stable. These results suggest that it not necessary to model the visual geometry accurately and suggest circumstances when tracker drift can be corrected by jumps in the display which will pass unnoticed by the user.
Harris, L. R., Jenkin, M., Zikovtiz, D., Redlick, F., Jaekl, P., Jasiobedzka, U., Jenkin, H., Allison, R. S., Simulating self motion I: cues for the perception of motion, Virtual Reality, 6: 75-85, 2002.
When people move there are many visual and non-visual cues that can inform them about their movement. Simulating self motion in a virtual-reality environment thus needs to take these non-visual cues into account in addition to the normal high-quality visual display. Here we examine the contribution of visual and non-visual cues to our perception of self-motion. The perceived distance of self motion can be estimated from the visual flow field, physical forces or the act of moving. On its own, passive visual motion is a very effective cue to self motion, and evokes a perception of self motion that is related to the actual motion in a way that varies with acceleration. Passive physical motion turns out to be a particularly potent self motion cue: not only does it evoke an exaggerated sensation of motion, but it also tends to dominate other cues.
Allison, R. S., Harris, L. R., Hogue, A., Jasiobedzka, U., Jenkin, H., Jenkin, M., Jaekl, P., Laurence, J., Pentile, G., Redlick, F., Zacher, J., Zikovitz, D., Simulating self motion II: A virtual reality tricycle, Virtual Reality, 6: 86-95, 2002.
When simulating self motion, virtual reality designers ignore non-visual cues at their peril. But providing non-visual cues presents significant challenges. One approach is to accompany visual displays with corresponding real physical motion to stimulate the nonvisual motion-detecting sensory systems in the natural way. However, allowing real movement requires real space. Technologies such as head mounted displays (HMDs) and CAVE TMs can be used to provide large immersive visual displays within small physical spaces. It is difficult, however, to provide virtual environments that are as large physically as they are visually. A fundamental problem is that tracking technologies that work well in a small, enclosed environment do not function well over longer distances. Here we describe Trike - a 'rideable' computer system that can be used to present large virtual spaces both visually and physically and thus provide appropriately matched stimulation to both visual and non-visual sensory systems.
Jenkin, M., and Dymond, P., Secure communication between lightweight computing devices over the internet, Proc. HICSS'02, 2002.
The odvent of light, low-power handheld computer devices such as windows ce, palm and handspring, is changing the way in which mobile users interact with their home office. These devices can be connected to the internet through both physical and wireless connections, and sensitive data transferred to and from these devices are subject to interception by a third party. Real-time encryption/decryption of data in handheld computers is complicated by the limited computing power availabel in these devices. In this paper we describe a method for secure transmission of data between remote handheld devies and other users on the internet. The system relies on one-time-pad technology which is ideally suited for handheld computing. The process of encrypting/decrypting data requires very little computation, and the generation of the random pads can be accomplished outside of the handheld devices. A prototype system is described which permits secure transmission of data through IR, radio ethernet, or physical connection.
Jaekl, P. M., Allsion, R. S., Harris, L. R., Jenkin, H. L., Jenkin, M. R., Zacher, J. E. and Zikovitz, D. C. Judging perceptual stability during active rotation and translation in various orientations. [Abstract] J. of Vision, 2: 508a, 2002.
Translation and rotation are detected by different patterns of optic flow and by different divisions of the vestibular system. A given movement (eg. yaw rotation or up/down translation) involves different sensors depending on the orientation of the movement with respect to gravity. Here we assess the contribution of these different sense systems to the "whole system" response to self motion. Our subjects' task was to distinguish self produced from external visual motion during rotation around the yaw, pitch and roll axes and during translation in the x (naso-occipital), y (sideways) and z (up and down) directions. The axis or direction of motion was parallel or orthogonal to the direction of gravity.Subjects wore a helmet-mounted display whose position was monitorred by a mechanical head tracker with minimal lag. The visual display was modified in response to head movement. The ratio between head and image motion was varied randomly using the method of constant stimuli. Subjects indicated whether the display appeared earth-stationary or not.For both rotation and translation there was a large range of ratios that was tolerated as perceptually stable. The ratio most likely to be accepted as stable corresponded to visual motion being faster than head motion. For rotation there were no consistent differences between yaw, pitch or roll axes and the orientation of the axis relative to gravity also had no effect. For translation motion in the x direction was on average matched with less visual motion than y or z motion. Although there was no consistent effect of whether motion was parallel or orthogonal to gravity, posture, relative to gravity, did have an effect.
Jenkin, M. and Tsotsos, J. K., Large-scale, touch-sensitive video display. United States Patent US 6,377,228. April 23, 2002
A video surface is constructed by adjoining a large number of flat screen display devices together. Superimposed over this surface is a tiling of transparent touch-sensitive screens which allow for user input. Thhe resulting display is thin, has a very high resolution, appears to be a single large screen to the user, and is capable of supporting many different types of human-machine interaction.
Harris, L. R., Allison, R. S., Jaekl, P. M., Jenkin, H. L., Jenkin, M. R., Zacher, J. E. and Zikovitz, D. C. Extracting self-created retinal motion. [Abstract] J. of Vision 2: 509a, 2002.
INTRODUCTION. Self movement generates retinal movement that is perceptually distinct from other movement. There are two types of models for how this distinction might be achieved. In the first, after self motion is detected, an internal estimate of the expected retinal movement is subtracted (a linear process) from retinal image movement. Remaining movement is interpretted as indicating external movement. In the second model, subjects internally compare observed visual motion with their internal representation: a non-linear ratio judgement which depends on the magnitude of the expected movement. A discriminable difference indicates external movement. These models respectively predict linear and non-linear distributions of the probability of regarding a given retinal motion as perceptually stable. METHODS. Our subjects' task was to distinguish self-produced from external visual motion during rotation around the yaw, pitch and roll axes and during translation in the x, y and z directions. They wore a helmet-mounted display whose position was monitorred by a mechanical head tracker with minimal lag. The visual display was modified in response to head movement. The ratio between head and image motion was adjusted by the subject until the display appeared earth-stationary. RESULTS. The distribution of ratios judged to be perceptually stable were fitted with a normal and a log normal distribution. For the rotation data a better fit was found using the log normal distribution suggesting that the non-linear ratio model is a better description of the underlying neural computations involved. No clear difference was found for the translation data.
