Designing virtual environments for usability
This thesis investigates user interaction in virtual environments and usability requirements to support that interaction. Studies of the design and use of virtual environments are used to demonstrate the need for interface design guidance. A theory of interaction for virtual environments is proposed, which includes predictive models of interactive behaviour and a set of generic design properties for supporting that behaviour. The models elaborate on D.A. Norman's cycle of action to describe the stages involved in three modes of behaviour: task and action based, exploratory and reactive. From the models, generic design properties are defined for various aspects of the virtual environment, such as its objects, actions and user representation. The models of interaction are evaluated through empirical studies of interactive behaviour which compare observed interaction patterns with those predicted. The generic design properties are evaluated through usability studies that investigate the links between missing design properties and usability problems encountered. Results from the evaluation studies provide general support for the theory and indicate specific refinements required. A controlled study is used to test the impact of the theory on interaction success, by comparing performance in virtual environments with and without implementation of the generic design properties. Significant improvements in interaction are found with the use of a virtual environment, after the predicted design properties have been implemented. Design guidelines are then developed from the theory and a hypertext tool designed to present the guidelines. The tool and guidelines are evaluated with industrial virtual environment designers to test the usability and utility of the guidance. Results indicate that the guidance is useful in addressing the practical problem of designing virtual environments for usability. Therefore, this thesis fulfils its objective of developing interface design guidelines for virtual environments, using interaction modelling as a theoretical base. Furthermore, it provides an improved understanding of user interaction in virtual environments and can be used to inform further theories, methods or tools for virtual environments and human-computer interfaces.