Adrian J. West

Aviary: Design issues for future large-scale virtual environments

VR is already evolving away from single user small-scale demonstrators, and inexorably toward sophisticated environments in which many geographically distributed users can perform a diverse range of activities. There will therefore be a pressure to make such environments increasingly general purpose and dynamic in their support of applications, paralleling perhaps the historical evolution of conventional operating systems. It is from speculations about the nature of such a future large-scale VR system that the AVIARY project has developed. AVIARY provides multiple worlds, each with its own set of laws, that may be tailored to suit particular application domains. The overall structure enables a coherent relationship between worlds to be maintained, which is important both for purposes of code reuse, and to aid users in navigating the system. A prototype implementation exists that addresses underlying implementation issues in the AVIARY model, and, in particular, distribution across heterogeneous processor networks, dynamic management of objects and message types within the system, the separation of graphics processing, and the management of spatial extent. Implementations of the prototype have been tested on a Transputer array, and a heterogeneous network of Sun and Silicon Graphics workstations. The system is currently being ported to a 2.4-Gflop KSR-1 parallel supercomputer. This paper reviews approaches to distributed, multi-application VR systems, presents pertinent elements of the AVIARY design, and describes the prototype implementation with particular attention given to the issues of distribution.

DEVA3: architecture for a large-scale distributed virtual reality system

In this paper we present work undertaken by the Advanced Interfaces Group at the University of Manchester on the design and development of a system to support large numbers of geographically distributed users in complex, large-scale virtual environments (VEs).We shown how the problem of synchronisation in the face of network limitations is being addressed by the Deva system through the exploitation of subjectivity. Further, we present a model for flexibly describing object behaviours in the VEs.Applications of the system in use are described.

AVIARY – A Generic Virtual Reality Interface for Real Applications

This paper introduces the work of the Advanced Interfaces Group at the University of Manchester, which is applying recent innovations in the field of human–computer interaction to important real-world applications, whose present human–computer interfaces are difficult and unnatural. We begin with an analysis of the problems of existing interfaces, and present an overview of our proposed solution – AVIARY, the generic, hierarchical, extensible virtual world model. We describe a users’ conceptual model for AVIARY, implementation strategies for software and hardware, and the application of the model to specific real-world problems.

Design issues for virtual reality systems

In this paper we describe a number of issues which are central to the design of a software architecture for a distributed, generic, virtual reality system. These include support for diverse and demanding applications, the management of time to provide high-quality interaction with tightly controlled closed-loop feedback, and the need for continuity of the experience presented to the user. These issues are being addressed in the design of a generic VR system called AVIARY.

Gnu/Maverik: A Microkernel for Large-Scale Virtual Environments

This paper describes a publicly available virtual reality (VR) system, GNU/MAVERIK, which forms one component of a complete VR operating system. We give an overview of the architecture of MAVERIK, and show how it is designed to use application data in an intelligent way, via a simple, yet powerful, callback mechanism that supports an object-oriented framework of classes, objects, and methods. Examples are given to illustrate different uses of the system and typical performance levels.

Navigation, Wayfinding, and Place Experience within a Virtual City

We report a qualitative study of navigation, wayfinding, and place experience within a virtual city. Cityscape is a virtual environment (VE), partially algorithmically generated and intended to be redolent of the aggregate forms of real cities. In the present study, we observed and interviewed participants during and following exploration of a desktop implementation of Cityscape. A number of emergent themes were identified and are presented and discussed. Observing the interaction with the virtual city suggested a continuous relationship between real and virtual worlds. Participants were seen to attribute real-world properties and expectations to the contents of the virtual world. The implications of these themes for the construction of virtual environments modeled on real-world forms are considered.

Performance of a skilled motor task in virtual and real environments

Three experiments compared the performances of adult participants (three groups of 10) on a perceptuo-motor task in both real world (RW) and virtual environments (VEs). The task involved passing a hoop over a bent wire course, and three versions of the task were used: a 3-D wire course with no background, a flattened version of the 3-D course (2½-D course) with no background, and the 2½-D course with added background to provide spatial context. In all three experiments the participants had to prevent the hoop from touching the wire as they moved it. In the first experiment, the VE condition produced about 18 times more errors than the RW task. The VE 2½-D task was found to be as difficult as the 3-D, and the 2½-D with the added background produced more errors than the other two experiments. Taken together, the experiments demonstrate the difficulty of performing fine motor tasks in VEs, a phenomenon that has not been given due attention in many previous studies of motor control in VEs.

Teallach: a model-based user interface development environment for object databases

Model-based user interface development environments show promise for improving the productivity of user interface developers, and possibly for improving the quality of developed interfaces. However, model-based techniques have rarely been applied to the important area of database interfaces. This lack of experience with data intensive systems may have led to model-based projects failing to support certain requirements that are essential in data intensive applications, and has prevented database interface developers from benefiting from model-based techniques. This paper presents a model-based user interface development environment for object databases, describing the models it supports, the relationships between these models, and the tool used to construct interfaces using the models.

System Challenges for Collaborative Virtual Environments

According to Professor Fred Brooks, virtual environment (VE) research has reached a point where it “barely works” (Brooks, 1999). We interpret this to mean that, although the technology has advanced to a point where many things are possible, there are still inadequacies which prevent its application to real-world problems. This difficulty of getting virtual reality (VR) to work adequately is due to a wide range of things: some are hardware-related, some depend on better algorithms and techniques, and yet others are related to human factors issues. This very diversity has led to some fragmentation in research: different groups study focused, tractable problems; solutions for one problem do not necessarily integrate easily with others, and technological limitations often frustrate attempts to scale up the results for larger real-world tasks. Gluing together the solutions for individual components of the problem is not guaranteed to work, and we can see evidence that the overall task is hard from the lack of convincing industrial-strength examples. Finding a solution for a real-world problem requires that diverse ideas and solutions be combined in some way. Before VR can move from a research-based subject into mainstream applications, ways must be found to integrate ideas from the contributing disciplines into a coherent architectural framework, designed to support systematic application development. Our own work, which is briefly touched upon in this chapter, is concerned with deriving such a system architecture.

Subjectivity and the relaxing of synchronization in networked virtual environments

Lag in network technology prevents absolute synchronization of distributed Virtual Environments (VEs); our experience of them is in this sense inherently subjective. We describe how subjectivity of this kind provides a means of enabling coherent shared experience in a VE, and present an architecture based on this.