A Low-Latency Display System with Delayed Viewport Mapping and Prioritized Rendering

Dr. Ronald Pose

Department of Computer Science, Monash University, Melbourne, AUSTRALIA


Immersive interactive computer graphics is a new paradigm for human-computer interaction. While various implementation strategies have been devised, they have generally employed traditional computer graphics techniques and in most cases have been found wanting. A new way of thinking about the problem is needed in order to deal with the tremendous difficulties, especially those involving the latency in responding to user orientation and position changes. In our approach we have drawn inspiration from the ancient Greek astronomical models and avoided some of the pitfalls others have have encountered.

Most researchers using such systems have recognized that latency in response to user orientation and positional changes is one of the most serious obstacles to successful immersion in virtual worlds. Excess latency can lead to serious user disorientation and even motion sickness. The problem has proved fairly intractable even using expensive machines which have tended to throw more and more computational power at the problem or have reduced image resolution with its attendant problems.

We have achieved the theoretical limit for response to orientation changes and have also allowed for dramatic reductions in the computational requirements for handling translation in the virtual world. This has been achieved by producing a novel graphics hardware architecture employing Delayed Viewport Mapping, which is targeted to interactive high resolution Virtual Reality applications but has much wider applicability. This architecture enables a new technique, Prioritized Rendering, to be performed, which takes advantage of image composition to provide better than linear performance improvement with multiple rendering engines. In this presentation the concepts behind a low-latency interactive graphics display device employing Delayed Viewport Mapping are described. The use of this hardware to enable image composition techniques to be applied to Virtual Reality style applications is explained. The concept of Prioritized Rendering is introduced and the principles behind its operation are explained.

The focus will be on the conceptual framework for this innovative technology, the basic geometric principles on which it is based, and a qualitative feeling for how the system can be exploited to provide orders of magnitude more performance than conventional systems. No detailed computer graphics background is required to understand the basic ideas.