40.6. Z-Sorting, Shading, and Further Topics

You've learned a huge amount about 3D graphics in a small space and put the essentials in place for a decent 3D engine. In this final section, I'll speed up a bit and introduce some topics for further research.

40.6.1. Polygon Z-Sorting

In "Backface Culling," you saw that backface culling removes faces that point away from you, hiding what would otherwise be overlapping portions of convex objects. However, even an object as simple as the torus in Example 40-5 overlaps itself in places despite backface culling, and more complex objects are likely to have problems as well. Backface culling is still a great optimization, because figuring out that a polygon is facing away takes far, far less time than drawing it to the screen, but the real solution to overlapping polygons is to sort them by their distance from the viewport.