model that will support a variety of image-synthesis algorithms, as well as nongraphics tasks.

This architectural transformation presents both opportunities and challenges. For hardware designers, the primary challenge is to balance the demand for greater programmability with the need to continue delivering high performance on traditional image-synthesis algorithms. Software developers have an opportunity to escape from the constraints of hardware-dictated image-synthesis algorithms so that almost any desired algorithm can be implemented, even those that have nothing to do with graphics. With this opportunity, however, comes the challenge of writing efficient, high-performance parallel software to run on the new graphics architectures. Writing such software is substantially more difficult than writing the single-threaded software that most developers are accustomed to, and it requires that programmers address challenges such as algorithm parallelization, load balancing, synchronization, and management of data locality.

The transformation of graphics hardware from a specialized architecture to a flexible high-throughput parallel architecture will have an impact far beyond the domain of computer graphics. For a variety of technical and business reasons, graphics architectures are likely to evolve into the dominant high-throughput “manycore” architectures of the future.

This article begins by describing the high-level forces that drive the evolution of realtime graphics systems, then moves on to some of the detailed technical trends in realtime graphics algorithms that are emerging in response to these high-level forces. Finally, it considers how future graphics architectures are expected to evolve to accommodate these changes in graphics algorithms and discusses the challenges that these architectures will present for software developers.

 

APPLICATIONS DRIVE EVOLUTION OF GRAPHICS ARCHITECTURES To understand what form future graphics architectures are likely to take, we need to examine the forces that are driving the evolution of these architectures. As with any engineered artifact, graphics architectures are designed to deliver the maximum benefit to the end user within the fundamental technology constraints that determine what is affordable at a particular point in time. As VLSI (very large-scale integration) fabrication technology advances,

the boundary of what is affordable changes, so that each generation of graphics architecture can provide additional capabilities at the same cost as the previous generation. Thus, the key high-level question is: What do we want these new capabilities to be?

Roughly speaking, graphics hardware is used for three purposes: 3D graphics, particularly entertainment applications (i.e., games); 2D desktop display, which used to be strictly 2D but now uses 3D capabilities for compositing desktops such as those found in Microsoft’s Vista and Apple’s Mac OS X; and video playback (i.e., decompression and display of streaming video and DVDs).

Although for most users desktop display and video playback are more important than 3D graphics, this article focuses on the needs of 3D graphics because these applications, with their significant demands for performance and functionality, have been the strongest force driving the evolution of graphics architectures.

Designing a graphics system for future 3D entertainment applications is particularly tricky because at a technical level the goals are ill defined. It is currently not possible to compute an image of the ideal quality at real-time frame rates, as evidenced by the fact that the images in computer-generated movies are of higher quality than those in computer games. Thus, designers must make approximations to the ideal computation. There are an enormous variety of possible approximations to choose

L ink between Applications and Architectures

short-term influence

graphics
architectures

graphics
applications

medium-term influence