PixelFlow: high-speed rendering using image composition

Abstract

We describe PixelFlow, an architecture for high-speed image generation that overcomes the transformation- and frame-buffer-access bottlenecks of conventional hardware rendering architectures. PixelFlow uses the technique of image composition: it distributes the rendering task over an array of identical renderers, each of which computes a full-screen image of a fraction of the primitives. A high-performance image-composition network composites these images in real time to produce an image of the entire scene. Image-composition architectures offer performance that scales linearly with the number of renderers; there is no fundamental limit to the maximum performance achievable using this approach. A single PixelFlow renderer rasterizes up to 1.4 million triangles per second, and an n-renderer system can rasterize at up to n times this basic rate. PixelFlow performs antialiasing by supersampling. It supports deferred shading with separate hardware shaders that operate on composited images containing intermediate pixel data. PixelFlow shaders compute complex shading algorithms and procedural and image-based textures in real-time. The shading rate is independent of scene complexity. A PixelFlow system can be coupled to a parallel supercomputer to serve as an immediate-mode graphics server, or it can maintain a display list for retained mode rendering. The PixelFlow design has been simulated extensively at high level. Custom chip design is underway. We anticipate a working system by late 1993.