Leonard McMillan Jr. An Image-Based Approach to Three-Dimensional Computer Graphics (Under the direction of Gary Bishop) The conventional approach to three-dimensional computer graphics produces images from geometric scene descriptions by simulating the interaction of light with matter. My research explores an alternative approach that replaces the geometric scene description with perspective images and replaces the simulation process with data interpolation. I derive an image-warping equation that maps the visible points in a reference image to their correct positions in any desired view. This mapping from reference image to desired image is determined by the center-of-projection and pinhole-camera model of the two images and by a generalized disparity value associated with each point in the reference image. This generalized disparity value, which represents the structure of the scene, can be determined from point correspondences between multiple reference images. The image-warpi...

The field of view (FOV) in most head-mounted displays (HMDs) is no more than 60 degrees wide -- far narrower than our normal FOV of about 200 wide. This mismatch arises mostly from the difficulty and expense of building wide-FOV HMDs. Restricting a person's FOV, however, has been shown in real environments to affect people's behavior and degrade task performance. Previous work in virtual reality too has shown that restricting FOV to 50 or less in an HMD can degrade performance. I conducted experiments with a custom, wide-FOV HMD and found that performance is degraded even at the relatively high FOV of 112, and further at 48. The experiments used a prototype tiled wide-FOV HMD to measure performance in VR at up to 176 total horizontal FOV, and a custom large-area tracking system to establish new findings on performance while walking about a large virtua...

We introduce and present preliminary results for a hybrid display system combining head-mounted and projector-based displays. Our work is motivated by a surgical training application, where it is necessary to simultaneously provide both a high-fidelity view of a central close-up task (the surgery) and visual awareness of objects and events in the surrounding environment. In particular, for trauma surgeons it would be valuable to learn to work in an environment that is realistically filled with both necessary and distracting objects and events. In this paper, we motivate the use of a hybrid display system, discuss previous work, describe a prototype along with methods for geometric calibration, and present results from a controlled human subject experiment. 1.

. A paradigm for the design of systems that manage level of detail in virtual environments is proposed. As an example of the prototyping step in this paradigm, a user study was performed to evaluate the effectiveness of high detail insets used with head-mounted displays. Ten subjects were given a simple search task that required the location and identification of a single target object. All subjects used seven different displays (the independent variable), varying in inset size and peripheral detail, to perform this task. Frame rate, target location, subject input method, and order of display use were all controlled. Primary dependent measures were search time on trials with correct identification, and the percentage of all trials correctly identified. ANOVAs of the results showed that insetless, high detail displays did not lead to significantly different search times or accuracies than displays with insets. In fact, only the insetless, low detail display returned significantly differ...

Fish tank VR systems provide head coupled perspective projected stereo images on a display device of limited dimensions that resides at a fixed location. Therefore, fish tank VR systems provide only a limited virtual workspace. As a result, such systems are less suited for displaying virtual worlds that extend beyond the available workspace and depth perception problems arise when displaying objects (virtually) located on the edge of the workspace in between the viewer and the display screen. In this paper we present two techniques to reduce this disadvantage: cadre viewing and amplified head rotations. The first aims to eliminate the problems in depth perception for objects with negative parallax touching the screen surround. Subjective observations from an informal user study indicate a reduction of confusion in depth perception. The second provides a transparent navigation technique to allow users to view larger portions of the virtual world without the need for an additional input device to navigate. A user study shows it performs equally well when compared to a technique based on the use of an additional spatial input device. 1

This study compares three common strategies for handling collisions between the user's virtual body and other objects in a cluttered virtual environment. test subjects sought "treasures" in a maze of narrow corridors which were embedded in a jumble of irrelevant shapes. The application ran on a PC, with the mouse and screen as the interface. When encounters an object, he either passes through it, stops completely, or is deflected around it. Data show that the third strategy best facilitates goal-seeking behavior with this interface and for this type of problem. This result is significant because collision handling is critically important to the usefulness of Virtual Reality applications. Furthermore, the screen-and-mouse interface is both the most common and least studied for virtual environments.

As we move through the world, we get around most objects using low-level psycho-motor behaviors, which require little conscious thought. In most virtual reality (VR) applications, the user also needs to get around objects in a reasonable way. However, most interfaces provide neither the sensory input nor the body control for users to move about as they do in the real world. We studied three prototypical methods of collision handling in VR: Either the user goes through an object like a ghost, stops dead on contact, or slides around it. In two experiments, subjects used a screen-and-mouse interface to navigate clutter virtual mazes. We found that the third method, sliding, enables superior navigation. While it does not simulate human avoidance behaviors, it does model their effect in terms of object avoidance. Significantly, screen-and-mouse is the both the most used and least studied VR interface. INTRODUCTION Collision handling strategies for existing virtual environment (VE) based ...

The computational requirements of high-quality, real-time rendering exceeds the limits of generally available computing power. However illumination effects, except shadows, are less noticeable on moving pictures. Shadows can be produced with the same techniques used for visibility computations, therefore the basic requirements of real-time rendering are transformations, pre-selection of the part of the scene to be displayed and visibility computations. Transformations scale well, ie, their time requirement grows linearly with the input size. Pre-selection, if implemented by the traditional way of polygon clipping, has a growing rate of N log N in the worst case, where N is the total number of edges in the scene. Visibility computations, exhibiting a quadratic growing rate, are the bottleneck from a theoretical point of view. Three approaches are discussed to speed up visibility computations: (i) reducing the expected running time to O(N log N ) (ii) using approximation algorithms with ...

This document consists out of: Tracking Technology (1.2) which describes the extended virtual environment EVE, the vision based setup and the tracking of people in this environment, Simple Prototype Setup (1.3) describes the undersea prototype in EVE, followed by the the work between ZKM and EPFL on interface paradigms for linking real and virtual people (1.4 through 1.6). Document eRENA -- D 6.3 Type Deliverable report with video material Status Final Version 1.0 Date August 1999 Author(s) ZKM: Michael Hoch, Detlev Schwabe, Jeffrey Shaw, Heike Staff EPFL: Soraia Raupp Musse, Fabien Garat, Daniel Thalmann KTH: Kai-Mikael J-Aro, John M. Bowers, Sten-Olof Hellstrm Task 6.3 eRENA--D6.3 Individual and Group Interaction August 1999 ESPRIT Project 25379 - 2 - Table of Contents Preface.............................................................................................................................. 3 1. Technology for group Interaction Between Real and Virtual ............

Fish tank VR systems provide head coupled perspective projected stereo images on a display device of limited dimensions that resides at a fixed location. Therefore, fish tank VR systems provide only a limited virtual workspace. As a result, such systems are less suited for displaying virtual worlds that extend beyond the available workspace and depth perception problems arise when objects that are (virtually) located on the edge of the workspace in between the viewer and the display screen are displayed. In this paper we present two techniques to reduce this disadvantage: cadre viewing and amplified head rotations. Cadre viewing aims to eliminate the problems in depth perception for objects with negative parallax touching the screen surround. Subjective observations from an informal user study indicate a reduction of confusion in depth perception. Amplified head rotations provide a transparent navigation technique to allow users to view larger portions of the virtual world without the need for an additional input device to navigate. A user study shows it performs equally well when compared to a technique based on the use of an additional spatial input device.