Alan Murta

Interactive Rendering with Real-World Illumination

We propose solutions for seamlessly integrating synthetic objects into background photographs at interactive rates. Recently developed image-based methods are used to capture real-world illumination, and sphere-mapping is used illuminate and render the synthetic objects. We present a new procedure for approximating shadows cast by the real-world illumination using standard hardware-based shadow mapping, and a novel image composition algorithm that uses frame-buffer hardware to correctly overlay the synthetic objects and their shadows onto the background image. We show results of an OpenGL implementation of the algorithm that is capable of rendering complex synthetic objects and their shadows at rates of up to 10 frames per second on an SGI Onyx2.

Virtual environments for scene of crime reconstruction and analysis

This paper describes research conducted in collaboration with Greater Manchester Police (UK), to evalute the utility of Virtual Environments for scene of crime analysis, forensic investigation, and law enforcement briefing and training. We present an illustrated case study of the construction of a high-fidelity virtual environment, intended to match a particular real-life crime scene as closely as possible. We describe and evaluate the combination of several approaches including: the use of the Manchester Scene Description Language for constructing complex geometrical models; the application of a radiosity rendering algorithm with several novel features based on human perceptual consideration; texture extraction from forensic photography; and experiments with interactive walkthroughs and large-screen stereoscopic display of the virtual environment implemented using the MAVERIK system. We also discuss the potential applications of Virtual Environment techniques in the Law Enforcement and Forensic communities.

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.

Practical experience of run-time link reconfiguration in a multi-transputer machine

The paper describes a novel message passing regime for multi-processor machines using transputers. The development of this facillity was motivated by the disparity between the interconnect available in transputer machines and the arbitary degree of interconnect implicit in the underlying CSP model of computation. The technique presented involves the alteration of the link topology of the machine during run-time, under the contrl of executing user code. Performance evaluation has been undertaken and the results are given. In particular, it is shown how run-time reconfiguration leads to performance enhancement for some classes of problems.

Visualizing mobile robot sonar data using polygon set operations

Mobile robots commonly employ a variety of sensor in order to gather information about their immediate environment. Whereas some types of sensor produce a wealth of environmental information in a human-understandable for, it is often low-level data such as range-finder measurements which are of greatest interest to the operator. This paper describes an approach to the visualization of data form acoustic sensor which use echo-location to determine object distances. Acoustic distance measurement is problematic in that echoes may fail to be returned to the source, range assessments may be inaccurate, and ghost readings may also appear in the data. The visualization method described attempts to overcome the idiosyncrasies of acoustic sensing to present a relatively consistent representation of the robots spatial environment to the operator. It maintains a geometric model of the perceived environment, allowing ambiguities in the current sensor data to be identified. The model is updated using polygon set operations to incorporate new sensor readings. Two features are recorded: the extent of free space identified within the environment, and the location of any obstacles which have been detected. This visualization approach is also tolerant to inaccuracies in odometry measurement. An experimental application of the method is reported.