The Lazy Z-Buffer

This paper describes a new perspective on a fundamental algorithm of three-dimensional computer graphics, namely z-buffering. An implementation of the z-buffer method in a lazy functional language behaves in a quite different manner to the traditional imperative counterpart. The main result of this paper is to show that the lazy z-buffer is a scan-line method. The effective difference between scan-line methods and z-buffers is one of order of evaluation. A hybrid algorithm with properties common to both z-buffer and scan-line methods is also described.