This article concerns the benefits of presenting abstract data in 3D. Two experiments show that motion cues combined with stereo viewing can substantially increase the size of tbe graph that can be perceived. The first experiment was designed to provide quantitative measurements of how much more (or less) can be understood in 3D than in 2D. Tbe 3D display used was configured so that the image on the monitor was coupled to the user’s actual eye positions (and it was updated in real-time as the user moved) as well as being in stereo. Thus the effect was like a local “virtual reality ” display located in the vicinity of the computer monitor. The results from this study show that head-coupled stereo viewing can increase the size of an abstract graph that can be understood by a factor of three; using stereo alone provided an increase by a factor of 1.6 and bead coupling alone produced an increase by a factor of 2.2, Tbe second experiment examined a variety of motion cues provided by head-coupled perspective (as in virtual reality displays), hand-guided motion and automatic rotation, respectively, both with and without stereo in each case. The results show that structured 3D motion and stereo viewing both help in understanding, but that the kind of motion is not particularly important; all improve performance, and all are more significant than stereo cues. These results provide strong reasons for using advanced 3D graphics for interacting with a large variety of information structures.

Although systems for animating algorithms are becoming more powerful and easier for programmers to use, not enough attention has been given to the techniques that an algorithm animator needs to create effective visualizations. This paper reviews the techniques for algorithm animation reported in the literature thus far and introduces new techniques that we have developed for using color and, to a lesser extent, sound. The paper also presents six algorithm animations that illustrate the new techniques. A videotape of these animations is available.

This report describes a variety of 3D interactive graphics techniques for visualizing programs. The third dimension provides an extra degree of freedom for conveying information, much as color adds to black-and-white images, animation adds to static images, and sound adds to silent animations. The examples in this report illustrate three fundamental uses of 3D: for providing additional information about objects that are intrinsically two-dimensional, for uniting multiple views, and for capturing a history of execution. The application of dynamic three-dimensional graphics to program visualization is largely unexplored. A videotape of these animations is available.

Systems supporting the visualization and animation of algorithms, programs, and computations have focused primarily on two-dimensional graphics to date. In this paper we identify the need for three-dimensional graphics in these types of displays, and we describe how 3D imagery best can be used for visualizing computations. We also introduce an animation toolkit that supports simplified development of 3D computation visualizations. A few examples of computation visualizations created with the toolkit are described and included. Our methodology, although specifically applied to computation visualization, is general-purpose and can be used to build a variety of 3D information visualizations and animations. Keywords: information visualization, 3D computer graphics, program visualization, algorithm information, software understanding 1 Introduction For many years the primary way to understand a computer program's or process' execution was to examine its source code and utilize a debugge...

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The lambda calculus is a formal symbolic term rewrite system that has been used for many years both as a mechanism for defining the semantics of programming languages, and as the basis for functional programming languages. In this paper, we describe a completely visual representation for lambda expressions, VEX, that has several advantages over traditional textual lambda calculus. Although VEX is designed as an expression-oriented component of VIPR [3, 4], it can also be used in teaching the concepts of lambda calculus as a replacement for or augmentation to the teaching of traditional textual rewrite rules. Many semantic issues in lambda calculus that are confusing to students, including substitution, free variables, and binding, become apparent and explicit in VEX. 1.0 INTRODUCTION The lambda calculus is a widely used and powerful notation for describing computable functions. It serves as the basis of functional languages, and is also the basis of denotational semantics. In order to ...

this paper. It is important not only to "back up" variables to their previous values, but also to "back up" a consistent view of the user interface, including static code, dynamic data, and graphical output so that the user "backs up" their mental image of the program execution. The reversible control structure aspects of ZStep 95 are discussed in more detail in [9]. We will address the issue of the computational expense of the historykeeping mechanism later. ZStep 95's main menu uses a bi-directional "video recorder" metaphor. The single-arrow "play" and "reverse" correspond to single-step in a traditional stepper, and the "fast-forward" and "rewind" operation go from an expression to its value and vice versa, without displaying details.

This paper describes fractal approaches to the problems which associate with visualizing huge hierarchies. The geometrical characteristic of a fractal, selfsimilarity, allows users to visually interact with a huge tree in the same manner at every level of the tree. The fractal dimension, a measure of complexity, makes it possible to control the total amount of displayed nodes. A prototype visualization system for UNIX directories is also shown. 1 Introduction Visualization systems for hierarchical structures, especially for huge 1 data structures, have a potential usefulness. For example, the visualization of whole UNIX directories might help system administrators to maintain the file systems. Since administrators could recognize, through the visualization, local file systems of each computer and remote file systems mounted by using NFS (Network File System), they might avoid mistakes, such as deleting or moving files which are being referenced by other computers. It is, however, m...

Knowledge-based systems often represent their knowledge as a network of interrelated units. Such networks are commonly presented to the user as a diagram of nodes connected by lines. These diagrams have provided a powerful visual metaphor for knowledge representation. However, their complexity can easily become unmanageable as the knowledge base (KB) grows. This paper describes an alternate visual representation for knowledge structures, loosely inspired by a virtual environment approach to navigation. This representation uses nested boxes rather than linked nodes to represent relations. The intricate structure of the knowledge base is conveyed by a combination of position, size, color, and font cues. MUE (Museum Unit Editor) was implemented using this representation to provide a graphic front-end for the Cyc knowledge base. INTRODUCTION Cyc and Knowledge Representation The Cyc project [Lena88] is an effort to build a very large knowledge base that encompasses a broad range of common...

Program debugging can be an expensive, complex and frustrating process. Conventional programming environments provide little explicit support for the cognitive tasks of diagnosis and visualization faced by the programmer. ZStep 94 is a program debugging environment designed to help the programmer understand the correspondence between static program code and dynamic program execution. Some of ZStep 94's innovations include: • An animated view of program execution, using the very same display used to edit the source code • A window that displays values which follows the stepper's focus • An incrementally-generated complete history of program execution and output • "Video recorder " controls to run the program in forward and reverse directions and control the level of detail displayed • One-click access from graphical objects to the code that