Delay is an unavoidable reality in collaborative environments. We propose an approach to dealing with delay in which ‘decorators ’ are introduced into the interface. Decorators show the presence, magnitude and effects of delay so that participants can better understand its consequences and adopt their own natural coping strategies. Two experiments with different decorators show that this approach can significantly reduce errors in specific collaborative activities. We conclude that revealing delays is one way in which groupware can benefit from accepting and working with the reality of distributed systems, rather than trying to maintain the illusion of copresent interaction.

This paper provides a solution for predicting moving/moving and moving/ static collisions of objects within a virtual environment. Feasible prediction in real-time virtual worlds can be obtained by encompassing moving objects within a sphere and static objects within a convex polygon. Fast solutions are then attainable by describing the movement of objects parametrically in time as a polynomial. Key Words: real-time, collision detection, collision prediction, Voronoi diagram, distance function. 1 Introduction This paper advances a novel method of collision detection, first proposed in [Sandoz & Sharkey 1994], that performs in continuous time, rather than the prevalent discrete implementation of `frame rates'. The collision detection technique relies on time based object movement, defined parametrically to predict when collisions occur. Collision prediction is a basic component of a real-time predictive architecture for multi-user virtual worlds [Roberts & Sharkey 1995]. The central id...