Using IRIS Explorer as a Visualisation Web Server

by Jason Wood, Helen Wright and Ken Brodlie, University of Leeds

The World Wide Web (WWW) has been receiving an enormous amount of attention for some time due to the way in which it allows us all to share data spread between a variety of sites on the Internet. Over the past few months, it has also been used as a mechanism to distribute compute tasks and calculations across different locations as well. With the emergence of the de facto standard Virtual Reality Modelling Language (VRML) (External) we are now able to send 3D scenes and objects across the web for remote viewing of, amongst other things, visualised data.

We have been investigating the feasibility of creating a Visualisation Web Server based on IRIS Explorer (External) which uses these features. The architecture of the server includes a number of parts: a User Interface implemented using HTML and a web browser; a visualisation server which utilises IRIS Explorer as its visualisation engine; and a VRML browser for viewing the resulting visualisation. The user accesses the server as a page on the WWW; this is a form containing a number of fields to be set by the user which control not only the selection of the data to be visualised but also the visualisation parameters. On submission of the form a Common Gateway Interface (CGI) script is executed on the web server machine which extracts the information in the form. This in turn is passed to the visualisation server where it is used to set parameters in the map that is run by IRIS Explorer. The map is executed and the resultant geometry is given back to the visualisation server as an Inventor file. This server translates the Inventor file into VRML1.0 format, before being transferred back to the user's client, where it is delivered to an appropriate VRML browser. The diagram above illustrates the process.

We based the Visualisation Web Server on IRIS Explorer because its native format for geometry is Inventor. Since this is also the precursor of VRML it was particularly easy to produce VRML from IRIS Explorer.

The server idea has been demonstrated at Leeds as an education application for MSc students taking a visualisation module, to illustrate the way in which various visualisation techniques can be applied to data. The advantage of this way of working is that the student is free to concentrate on the results of applying a technique, rather than on the details of how it is invoked in the map. Another application we have developed is the visualisation over the WWW of air quality data, collected in real-time from a number of sites around the UK. More details of this application and the system in general are to be presented in a paper entitled "Visualization Over the World Wide Web and its Applications to Environmental Data" at IEEE Visualization '96.