David A. Southard

Transformations for stereoscopic visual simulation

Abstract Stereoscopic display devices are now standard offerings for graphics workstations. These displays find application in medical, scientific, and engineering visualization. Several geometric models can be used to determine the projections for stereoscopic images. In some circumstances, however, the perceived image may be uncomfortable to view, or it may contain undesirable depth distortions. We present a geometric model for stereoscopic viewing that can accurately model most viewing situations. Using this model, the viewer comfortably perceives realistic size and depth relationships among objects in the stereoscopic image. We relate this model to human visual constraints, and develop the geometric transformations required to use this method on graphics workstations.

Viewing model for virtual environment displays

We present a viewing model that is appropriate for several types of displays used in virtual environment systems, including head-mounted displays and head-tracked stationary displays. The model accounts for arbitrary size, placement, and orientation of the display images, and thus is suitable for various display designs. We provide algorithms for calculating stereoscopic viewing and projection matrices. The tracking algorithm models the position and orientation of the trackers emitter and the displacement between the sensor and the users eyes. The algorithms are presented as parameterized homogeneous transforms. We also discuss features that can be used to avoid accommodation/convergence conflicts. The advantages of this viewing model and algorithm are the elimination of possible vertical parallax, an undistorted perception of depth, and reduction of eye fatigue due to excessive parallax. All of these factors contribute to improved comfort and utility for the operator.

Piecewise planar surface models from sampled data

Interactive visualization of three dimensional data requires construction of a geometric model for rendering by a graphics processor. We present an automated method for transforming dense, uniformly sampled data grids to an irregular triangular mesh that represents a piecewise planar approximation to the sampled data. The mesh vertices comprise surface-specific points, which characterize important surface features. We obtain surface-specific points by a novel application of linear and non-linear filters, and thresholding. We define a procedure for constructing a triangulation, derived from a Delaunay triangulation, that conforms to the sampled data. In our example application, modeling a terrain surface over a large area, an 80% reduction in polygons maintains an acceptable fit. This method also extends to the tessellation of images. Applications include scientific visualization and construction of virtual environments.

Head-mounted displays for virtual reality

Head mounted displays (HMD) provide one means of displaying virtual environments. This paper assesses the state of HMD technology, with respect to the Virtual Reality (VR) goal of creating an environment which matches users experience with the real world. We find that current HMDs fall short in important characteristics, such as resolution, field of view, and physical attributes. A system designer, familiar with these limitations, should be able to provide a suitable immersive virtual environment with the inclusion of appropriate graphics rendering techniques and virtual environment input/output devices.

Viewing model for stereoscopic head-mounted displays

We characterize a class of stereoscopic displays, that includes head-mounted displays that incorporate miniature cathode-ray tubes. We present a detailed viewing model that accounts for the placement, size, and orientation of the virtual display images. The model is appropriate for several types of head-mounted displays, as well as head-tracked stationary displays. The tracking algorithm accounts for the displacement between the tracking sensor and the users eyes. We provide algorithms for calculating stereoscopic viewing and projection matrices. The algorithms are presented as parameterized homogeneous transforms. We also discuss design guidelines for avoiding accommodation/convergence conflicts, and managing the perceived field-of-view. The advantages of this viewing model and algorithm are the elimination of possible vertical parallax, and an undistorted perception of depth. Both of these factors can contribute to improved utility for the operator.

Compression of digitized map images

Abstract : The Air Force Mission Support System (AF MSS) will display digital images of navigational charts. The Defense Mapping Agencys (DMA) Equal Arc-Second Raster Chart (ARC) Digitized Raster Graphics (ADRG) products will be the primary source of data. System cost and performance goals require a storage reduction ratio of 48:1 for these images. This reduction will be obtained through a combination of spatial reduction, image compression, and color quantization. The AF MSS system specification admits many possible implementations at each step. Some combinations of options do not yield satisfactory results. This report describes a series of investigations into these three areas. We evaluate alternative algorithms, and identify a set of choices that offer the best image quality and performance, based on our prototype tests.

Stereoscopic displays for terrain database visualization

Stereoscopic displays enhance the ability of the viewer to comprehend spatial relationships. With the commercial introduction of liquid crystal stereoscopic shutters (LCSS), it has become practical to incorporate stereoscopic 3D into moderately-priced graphics workstations, greatly extending the applicability of this technique. This paper reports on the results of an evaluation of stereoscopic 3D for Air Force applications. This work focused on the identification and development of optimized stereoscopic display techniques for the visualization of terrain data.

A virtual environment architecture

Part of MITREs charter as a Federally Funded Research and Development Center (FFRDC) is to objectively evaluate and compare current technologies, and to recommend courses of action for numerous government programs. As such, the authors have been involved in assessing workstation, graphics, and user interface technology. They are currently developing a virtual environment architecture (VEA), to be used as a foundation for several prototype applications.<<ETX>>

Rapid modeling and design in virtual environments

We discuss the evolution and current status of investigations at our Graphics, Visualization, and Virtual Environments Laboratory. The progression of user interface technology has led us from display systems evaluation, to performance studies of graphics workstations, stereoscopic and head-mounted displays, user-input devices, and interactive techniques for virtual environments. We have been involved in prototyping applications for terrain visualization, situation awareness for command and control, maintenance procedures training, and interactive design. Our current emphasis is on developing techniques for rapid modeling of virtual environments, to support mission planning, rehearsal, and interactive design and visualization. We discuss in detail three examples of these applications, and we present a set of guidelines that we have found to be useful for quickly constructing effective virtual environments.

Vector quantization: a tool for exploration and analysis of multivariate images

We discuss how vector quantization, a technique well known for data compression, can be applied to exploratory data visualization. This technique is especially useful for multivariate imagery, because it reduces the data to a manageable size, without stripping important features. Previous visualization methods are able to combine up to three variables per pixel into an integrated display. Our vector quantization technique allows us to integrate essentially any number of variables per pixel. Furthermore, the cluster analysis inherent in vector quantization has the property of identifying relationships within the data, based on similarity of textural and sample features. We use straightforward techniques to visualize these relationships interactively. The result is a tool that applies to a wide variety of imagery visualization problems. Our prototype uses contrast enhancement, color scales, and highlighting for interactive feature extraction. We show examples from panchromatic and multispectral earth observation satellites and medical imagery.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.