Seminars & Events

Mathematics and Computer Science Division Seminar
"Parallax Barrier Autostereoscopic Virtual Reality Display Systems: From Varrier to Dynallax"

DATE: April 3, 2007
TIME: 10:30am
SPEAKER: Tom Peterka, PhD Candidate, University of Illinois at Chicago
LOCATION: Bldge: 221, Conference Room A216, Argonne National Laboratory
HOST: Susan Coghlan and Rob Ross

Description:
As scientific data sets increase in size, dimensionality, and complexity, new high resolution, interactive, collaborative networked display systems are required to view them in real-time. Increasingly, the principles of virtual reality (VR) are being applied to modern scientific visualization. Two of the tenets of VR are stereoscopic or 3D display and the sense of immersion or presence within the virtual world. However, these goals may conflict because the need to wear stereo glasses or other gear is encumbering and is a constant reminder of the artificiality of the experience, compared to the way that we interact with the real world. Moreover, devices such as head mounted displays, stereo shutter glasses, and polarized glasses hinder other positive aspects of VR such as collaboration by making face to face conversation and teleconferencing difficult as well as interfering with other routine tasks such as typing, etc. Autostereoscopic (autostereo) displays present imagery in 3D without the need to wear glasses or other gear, but few qualify as VR displays. We, at the Electronic Visualization Laboratory (EVL) at the University of Illinois at Chicago (UIC), have worked over the last six years to develop a family of high resolution glasses-free autostereo display systems utilizing both static and dynamic parallax barrier technology to produce a high quality viewing experience that qualifies as true VR.

Varrier is EVL’s name for the computational method and the family of systems based on a static parallax barrier. Since Varrier’s inception, new algorithmic and systemic developments have produced performance and quality improvements. Visual acuity has increased by a factor of 1.4X with new fine-resolution barrier strip linescreens and computational algorithms that support variable sub-pixel resolutions. Performance has improved by a factor of 3X using a new GPU shader-based sub-pixel algorithm that accomplishes in one pass what previously required three passes. The Varrier modulation algorithm that began as a computationally expensive task is now no more costly than conventional stereoscopic rendering. Head tracking is accomplished with a neural network camera-based tracking system developed at EVL for Varrier. Multiple cameras capture subjects at 120 Hz and the neural network recognizes known faces from a database and tracks them in 3D space. Varrier supports a variety of VR applications, including visualization of polygonal, ray traced, and volume rendered data. Both autostereo movie playback of pre-rendered stereo frames and interactive manipulation of 3D models are supported. Local as well as distributed computation is employed in various applications, and long-distance collaboration has been demonstrated with autostereo teleconferencing. Varrier has been deployed in a variety of form factors from large tiled installations to smaller desktop sizes, in a number of locations in the Chicago area as well as in San Diego, CA.

The newest research focuses on the use of a solid-state dynamic parallax barrier that affords features that were inconceivable with a static barrier. A dynamic barrier mitigates restrictions inherent in static barrier systems such as fixed view distance range, slow response to head movements, and fixed stereo operating mode. By dynamically varying barrier parameters in real time, viewers may move closer to the display and move faster laterally than with a static barrier system. Furthermore, the display can switch between 3D, 2D, and mixed modes by disabling the barrier on a per-pixel basis. Like Varrier, Dynallax is head-tracked, directing view channels to positions in space reported by a tracking system in real time. Such head-tracked parallax barrier systems have traditionally supported only a single viewer, but by varying the barrier period to eliminate conflicts between viewers, Dynallax presents four independent eye channels when two viewers are present. Each viewer receives an independent pair of left and right eye perspective views based on their position in 3D space. The display device is constructed using a dual-stacked LCD monitor where a dynamic barrier is rendered on the front display and the rear display produces a modulated VR scene composed of two or four channels. A small-scale head-tracked prototype VR system is demonstrated. Performance data are analyzed while advantages, disadvantages, ongoing and future work are identified. It is expected that Dynallax will be the foundation for the next generation of tiled walls capable of simultaneously displaying a variety of 3D modes such as tracked, untracked, single user, multi-user, as well as 2D content, flexibly interleaved on the same display canvas.

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