ERCIM News No.41 - April 2000 [contents]

Interactions in Virtual Environments

by Lakshmi Sastry and David Boyd

At CLRC Virtual Reality Centre, located at Rutherford Appleton Laboratory, work is underway to implement a 3D interaction toolkit as part of the INQUISITIVE project. The toolkit architecture has been derived from a task-based analysis of a range of immersive VR-based applications for large-scale engineering design reviews, operational training and scientific visualisation over the period of the last four years. A VR system specific subset of the toolkit is an Engineer’s Toolbox (ET) which is being developed as part of the smaller project Delivering Advanced Virtual Interactions to the Desktop (DAVID).

Virtual Reality (VR) technology and techniques have the potential to deliver intuitive user interfaces with more natural styles of interaction between the user and his application which will enhance productivity and performance. Facilities for user interface and interaction development within today’s VR systems are rudimentary, limited and limiting. The availability of a generic interaction toolkit with portable modules makes a significant contribution to the rapid development and successful application of 3D VR interaction techniques to a wide range of virtual environments.

The aim of the RAL component of the INQUISITIVE project is the development of a portable interaction toolkit for VR applications which will improve support for developing user interaction within task-oriented virtual environment applications. The design of the interaction toolkit is based on our extensive experience in developing and successfully deploying immersive end user applications for large scale engineering design reviews, operational training and visualization within virtual environments.

Toolkit Architecture

All application tasks, however complex, can be implemented in terms of a combination of tasks from the four basic classes of user interaction – navigation, selection, manipulation and data input, in virtual environments. Each basic interaction task can be realised using a number of possible interaction techniques. For example movement can be implemented using the magic carpet or point-fly techniques. Each application will identify one or more interaction techniques appropriate for carrying out the tasks required in that application. This in turn will guide the definition of the interaction processes needed to realise those techniques. The application tasks are then achieved by suitable combinations of these interaction processes. Based on this analysis, the main functional components which the toolkit must provide are:

The components of the runtime interaction framework are:

This architecture can be seen to map on to existing VR system kernels such as Maverik from the University of Manchester, UK and dvMockup from Parametric Technology.

Requirements Capture, Analysis and Modelling Methodology

We are using UML, the Universal Modelling Language, to capture and transform high level user interaction techniques and tasks into detailed interaction processes between the user, the system and the underlying application leading to an implementable design. The use case methodology is being used to identify the core classes that each basic interaction task will require and the derived classes and class variables and methods for each interaction technique. We have realised that even the simplest interaction process in VEs requires several agents co-operating together and monitoring various system states concurrently for task achievement. This places significant requirements on communication between the components of the interaction toolkit and between the interaction toolkit and the VR system manager. The interaction, activity and class diagrams are helping to clearly identify the appropriate classes and entities and how they collaborate within each process. Its ease of use and its ability to describe and analyse interaction processes from both the perspectives of user requirement and of communication between the user, the interaction toolkit, the VR system and the user’s application is promising.

Proof of Concept - An Engineer’s Toolbox

Over the past four years we have developed many VR-based applications for engineering design review, operational training and computational data visualisation in collaboration with other departments as part of supporting RAL’s engineering and scientific activities. The figure shows the VR model of the Atlas Inner Detector with lines-of-sight laid out to check clearance and clashes. Such applications have demonstrated the potential of virtual reality technology and interaction techniques to deliver cost effective productivity benefits and greater insight into engineering design and computational data. The utility of the INQUISITIVE Interaction Toolkit is to be realised via the DAVID project to deliver an application toolkit to the engineers and scientists so that use of VR becomes part of their design and analysis methodology. Thus the aim of the DAVID project is to develop a portable ‘virtual engineering toolbox’ which will include intuitive handling operations on model parts for simulation of assembly and maintenance tasks as well as sets of tools for measurements and alignment checking tasks in immersive and desktop environments. In addition, it can include facilities for superimposing and visualising analytical results from computational simulations such as metal deformation, fluid flow, thermal and stress analysis simulations. The implementation is currently under progress using the commercial VR system dvMockup which links closely with the ProEngineer CAD software.


Please contact:
Lakshmi Sastry - CLRC
Tel: +44 1235 44 6892