R-Buffer: A Pointerless A-Buffer Hardware Architecture

Abstract

We present a graphics hardware architecture that implements Carpenter's A-buffer. The A-buffer is a software renderer that uses pointer based linked lists. Our pointerless approach computes order independent transparency for any number of layers with minimal hardware complexity. Statistics are shown for a variety of different scenes using a trace based methodology, with an instrumented Mesa OpenGL implementation. The architecture is shown to require from 2.1 to 3.6 times more memory than traditional Z-buffering. A detailed hardware design is provided, Order independent transparency is computed without application sorting and without artifacts. The architecture can also be used for antialiasing, and an example of Carpenter's classical A-buffer antialiasing is shown.