Multi-user Virtual Reality System "MAARE":
Design and Implementation

Abstract

The more computers are connected with networks, the more of their role is changed from a tool extending individual ability into an environment which supports the sharing of each individual's ability and knowledge. MOO (Multi-user dungeon, Object Oriented) is one of such environments. This system is built with server-client model. Users can exchange information and work cooperatively with shared time and virtual places, which is provided by MOO after they log on. In the virutual places, users can built virtual objects and methods and store them to the database in server. MOO is also an experimental environment of a virtual community or society.

Though MOO has a variety of potentials, it only deals text-based information. This constraint prevents it to be used in the development of certain types of applications which are often used to suport cooperative work, like shared drawing tools, shared text editors or video conference systems. There has been some research aimed at solving the problem, some of which make it possible for users to talk to each other with live video and sound. However, these approaches tend to create new constraints, for example, allowing the virtual world to be built only with 3D computer graphics. There are two approaches in virtual reality research. One is to make an imitation or a simulation of the real world in it, and the other is to make a brand new world which suits the nature of virtual reality. The latter can create a world and reality newly generated with computers, which none of us have ever experienced. This is called Another Reality.

In this research, another reality-oriented virtual reality system "MAARE" was designed with an aim of getting rid of the constraints of MOO, and then the prototype was implemented. MAARE has a same function as MOO, and also has a new added function that enables clients to contains any kinds of information in addition to MOO's, like text, image, sound, video, a variety of graphical user interface components, changeable on action of objects in virtual world. It also enables users to describe a virtual world with the user interface components they wish. Its mechanism is provided with the client which can load program from any server of World Wide Web (WWW), and which can execute it. The client can also make connections to any network resource. It provides abilities of inter-clients communication and client's information retrival directly from WWW. Thus users can build virtual world freely with user-level scripting both objects in server and programs loaded by clients. The prototype's server is implemented by adding some modification to MOO server system which is available as a freeware. The client is implemented with Java Language which already has security function. Test application software runnable on the prototype was created and a qualitative evaluation was done. As a result, it became clear that MAARE's functions and expressive power are superior to ones of other systems, and that it can provide an effective infrastructure for the research of Another Reality.