If you have not yet bought a copy of Flights Of Fantasy, and you would like a great introduction to 3D graphics, then rush right out to the nearest bookstore and pick up a copy. The Z-buffer algorithm, invented by E. Catmull, has been around since the 1970's. Because of it's simplicity, and because it can handle just about any 3D primitive, it has become the number one choice for hardware accelerated 3D boards. For the most part, object- precision algorithms tend to be fairly independent of the size of the viewport. On the other hand, image-precision algorithms are directly dependent on the size of the viewport.
Some methods require polygons to be non-intersecting.
Others require that all polygons in the world remain stationary. The Z-buffer algorithm imposes no such limitations. As a matter of fact, the Z-buffer imposes no limitations at all. It does require that you have a good amount of memory, and a fast processor though. The idea behind the Z-buffer algorithm is that you perform a test on every pixel of every polygon that you draw.