Adrian F Clark

VASE Laboratory
University of Essex

VRML, the Virtual Reality Modelling Language, is widely used to:

• provide a valuable way of visualizing numeric data and 3D objects
• form the basis of shared spaces

We are interested in using VRML for something a little different: to provide interfaces to information systems. This is because we think they have the potential for providing much more natural human-computer interaction.

• Like most universities, Essex has a Web-based information system. Navigating through the information can be difficult!

• Essex is sited on a single campus, so when VRML first appeared, it was natural to think of modelling the campus and using it as an alternative front-end to our information system.

• Each building typically houses a single department, so it is easy to make the buildings act as links to individual departments' Web pages.

• The campus lies on gently-rolling parkland, with the main buildings set into a valley; hence, we needed to produce a fair representation of the ground contours. Being a "red-brick" university, the buildings can be constructed from polygons.

• Since the architect's drawings were not available in electronic form, we had to resort to taking measurements from the drawings. Hence, we used a program to generate the VRML model.

• We took spot-heights from a 1:1,250 map, yielding 20 x 16 samples. We wrote a Tcl script to read those values and generate a 3D model consisting of triangles.

• The positions of the corners of buildings were measured and entered, along with the buidings' heights. The same Tcl script made the buildings stand on the ground model.

• Since the model is a schematic interface, features such as windows, covered walkways, etc were omitted. Roads, lakes etc consist of polygons at a height of 1m!

BT also use VRML models to front their innovative Portal site. This also features a VRML model of the site -- in fact, they were the first to do it anywhere in the world.

• One of my student projects built a VRML-based link visualizer as part of a larger Web management system.

• Here, blue cubes denote links that are verified as existing and red cubes links that are invalid. In the full system, clicking on a blue cube expands the links from that node.

• Local theatre and arts groups are trying to convert a disused building into a small theatre and approached us to help visualize how it would look.

• Having learned from our campus model, we built the theatre model (again from drawings) using higher-level primitives, again via a Tcl script.

• We realized that the script could be interfaced to a seat-booking system via CGI scripts, with seats colour-coded as to whether or not they were booked.

• This means that the model must be generated on the fly from information in the seat-booking database.

• Download time and rendering speeds are a problem because of texture-mapped "scenery."

• Clicking on a seat re-loads the model with a view of the stage from that seat. This is too slow!

• With VRML 2 we are able to download whether or not seats are booked into the VRML browser and use TouchSensors and scripts to handle interactions, making the system much more interactive. A Billboard can be used to present buttons, allowing the booking to be completed or discarded.

• The active badge system produced by the Computing Laboratory of the University of Cambridge and commercialized by the Olivetti & Oracle Research Laboratory allows, among other things, the locations of people to be tracked.

• These locations can be visualized in several ways, including VRML.

• One of the things that is currently receiving a great deal of thought is the use of VRML as the basis of multi-user networked games.

• We've been looking into this a little by attempting to produce a shared, VRML 2 version of the classic adventure game.

• There are similarities between this and the previous examples, since the rooms and objects are generated on the fly on the basis of information stored in a "database."

• The same database allows textual descriptions to be produced, so that text-based players can compete with those having a VRML view.

  You are standing at the end of a road
  before a small brick building.  Around
  you is a forest.  A small stream flows
  out of the building and down a gully.
  > ENTER

  You are inside a building, a well-house
  for a large spring.  There are some
  keys on the ground here.
  > TAKE KEYS

  OK.
  > EXIT

  You are at the end of the road again.
  

• Our initial implementation is based around Sony's Community Place browser and multi-user server.

• The database of rooms and object locations resides on the server. Only the current room and adjacent rooms are downloaded into the user's client.

• TouchSensors are placed at the exits to initiate motion between rooms.

• Our initial approach is really too slow. We are now investigating whether compiling the database into the "adventure applet" downloaded into the Web browser; we anticipate this will be much quicker (though more memory-hungry).

• The current version of Sony's browser doesn't allow objects to be deleted, so we move them below the floor!

• One of the nice things about Adventure was the range of actions available.

• Some interactions can be simulated to some extent -- e.g., a heads-up display of actions available via a Billboard or the inventory command jumping to a special room.

• However, many commands are just impossible to implement with existing mouse-based interfaces: how, for example, can one wave an object? What we need is a browser input API.

• For interfaces to information systems, it is often necessary to generate VRML models from a database. Our programmed approach was initially an expedient, but we have found it to be flexible and it enables us to build geometrically-accurate models rapidly from primitives.

• For people working in Java, the excellent JVerge class library facilitates creating VRML models from other types of data.

• We are thinking of extending our Tcl-based approach to encompass behaviour in addition to geometry: this may allow us to generate both Java and VRMLScript from the same source, so that one world definition can be used to drive different browsers.

• VRML is an excellent medium for creating innovative user interfaces to information systems.

• For many such interfaces, the VRML descriptions must be generated from other information. We have found Tcl to be effective; for people working in Java, the JVerge package is a good starting point.

• Our experiments in converting Adventure to VRML 2 shows that this type of game can work, though not yet quickly enough. Better interfaces to the user's input devices are needed to make VRML-based gaming into reality.