GeoSheet

A Distributed Visualization Tool for Geometric Algorithms

Abstracts

Motivation and design goal

Users

Requirements

Design Approach and Architecture

Examples

A Concise Guide

Further information

Traditionally algorithm designers for geometric problems use worksheets to draw, to test and to verify their ideas; during the implementation or execution of an algorithm they also rely on worksheets to convince themselves that the implemented algorithm works correctly. This being a very tedious and frustrating task, it is thus desirable to have a computer-assisted Input/Output device so that this "drawing" and "visualization" can be facilitated.

In view of the lack of such tools for geometric algorithm designers we have developed a graphical user interface, called GeoSheet. The user can input data on a geosheet with the use of mouse, and invoke an algorithm. The output of the algorithm on the given input can be displayed in the input geosheet or possibly other geosheets. It is implemented in C++ under SunOS X-window based environment.

To minimize software development cycle we make heavy use of the concept of software reuse. We adopt object-oriented design, building on reliable existing software, and writing new components when needed. The contents of the geosheet, the display, is modified from that of XFIG. Users of XFIG will find its appearance familiar. One of the design goals is to make it widely accessible to most sites connected to the Internet. Thus GeoSheet is distributed in the sense that it can be executed at one site, while its Input/Output can be directed to a possibly different site over the network. The computed output obtained at one site can also be broadcast to machines on other sites, as long as the machines on the remote site have been opened to receive the output.

Users

The system is useful for algorithm designers who want to design algorithms to solve geometric problems. It can help to test ideas in the development stage, and can help with debugging during the implementation stage. It is also useful for practitioners to visualize how an algorithm performs on various input data, and for educators to interactively query/demonstrate by examples geometric properties with visualization.

Requirements

To run this, you need to have SunOS 4.0.3 and Motif 4.x for geosheet and demo programs. For those algorithm designers who would like to use our tool to aid their designs, we provide a high-level library, geoLEDA which is derived from LEDA, as the major interface and GeoSheet at this time. Using geoLEDA, the user can perform high level graphical I/O operations, similar to the Unix "printf" commands directly from the user program. For this kind of usage, algorithms are required to be implemented in C++. For non LEDA users, our basic GeoIPC message passing mechanism is also available. Users can easily customize geosheet graphical I/O operations on their data objects with the aid of GeoIPC. GeoIPC requires SunOS 4.X.

Design Approach and Architecture

A detailed description is now available as a technical report, GeoSheet:A Distributed Visualization Tool for Geometric Algorithms . Please contact D. T. Lee at dtlee@eecs.nwu.edu for further information.

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