Marc H. Brown

Graphical fisheye views of graphs

A fisheye lens is a very wide angle lens that shows places nearby in detail while also showing remote regions in successively less detail. This paper describes a system for viewing and browsing planar graphs using a software analog of a fisheye lens. We first show how to implement such a view using solely geometric transformations. We then describe a more general transformation that allows hierarchical, structured information about the graph to modify the views. Our general transformation is a fundamental extension to the previous research in fisheye views.

A system for algorithm animation

A software environment is described which provides facilities at a variety of levels for “animating” algorithms: exposing properties of programs by displaying multiple dynamic views of the program and associated data structures. The system is operational on a network of graphics-based, personal workstations and has been used successfully in several applications for teaching and research in computer science and mathematics. In this paper, we outline the conceptual framework that we have developed for animating algorithms, describe the system that we have implemented, and give several examples drawn from the host of algorithms that we have animated.

Exploring algorithms using Balsa-II

The use of the Balsa-II algorithm animation environment to investigate the dynamic behavior of programs is discussed. Balsa-II is examined first from a users perspective and then from a programmers perspective. Some related systems are briefly considered.<<ETX>>

Zeus: a system for algorithm animation and multi-view editing

Algorithm animation is a form of program visualization that is concerned with dynamic and interactive graphical displays of a programs fundamental operations. The paper describes the Zeus algorithm animation system. Zeus is noteworthy for its use of objects, strong-typing, parallelism, and graphical development of views. Also of interest is how the system can be used for building multi-view editors.<<ETX>>

Techniques for Algorithm Animation

Allowing a user to interact with dynamically changing graphical representations of algorithms or data structures may help in teaching, research, or systems programming.

Color and sound in algorithm animation

The techniques developed by M. M. Brown and R. Sedgewick (1985) in using the Balsa algorithm-animation system are reviewed. Techniques that focus on color and sound, areas just opening up in workstation-based interactive algorithm-animation systems, are described. Color is used for encoding the state of data structures, highlighting activity, trying multiple views together, emphasizing patterns, and making an algorithms history visible in a single static image. Sound is used for reinforcing visuals, conveying patterns, replacing visuals, and signaling exceptional conditions. The techniques are based on work done with the Zeus algorithm-animation system. Six screen dumps from six different algorithm animations that are representative of the was Zeus was used are presented.<<ETX>>

Perspectives on algorithm animation

Systems for animating algorithms have received considerable interest of late as effective means for understanding computer programs. Thus far, nothing has been reported in the literature concerning nature of the displays nor to what extent displays can be created automatically. This paper addresses these two issues. The first part presents a taxonomy of displays prevalent in algorithm animation systems; the second part uses the taxonomy to analyze those types of displays that can and cannot be created automatically from unmodified source code.

Algorithm animation using 3D interactive graphics

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.

Collaborative Active Textbooks: a Web-based algorithm animation system for an electronic classroom

The paper describes CAT, a Web-based algorithm animation system. CAT augments the expressive power of Web pages for publishing passive multimedia information with a full-fledged interactive algorithm animation system. It improves on previous Web-based algorithm animations by providing a framework that makes it easy to construct new animations, including those that involve multiple views. Because views of the same running algorithm may reside on different machines, CAT is particularly well-suited for electronic classrooms. This strategy is an improvement over the electronic classroom systems the authors are aware of which simply display the same X window on multiple machines. They believe their framework generalizes to electronic textbooks in arbitrary domains.

Obliq-3D: a high-level, fast-turnaround 3D animation system

Describes Obliq-3D, a high-level, fast-turnaround system for building 3D animations. Obliq-3D consists of an interpreted language that is embedded into a 3D animation library. This library is based on a few simple, yet powerful constructs that allow programmers to describe 3D scenes and animations of such scenes. By virtue of its interpretive nature, Obliq-3D provides a fast-turnaround environment. The combination of simplicity and fast turnaround allows programmers to construct nontrivial animations quickly and easily. The paper is divided into three major parts. The first part introduces the basic concepts of Obliq-3D, using a series of graduated examples. The second part shows how the system can be used to implement cone trees. The third part develops a complete animation of Dijkstras (1959) shortest-path algorithm. >