There’s a great article on Beyond3D about the technology of a 3D engine. The article’s split up into parts and part two was just released (after a several month wait!). Part one discusses a lot of the general concepts for a 3D engine design in an easy to read and abstract level, but part two goes into deeper detail. Both make for interesting reads, though part two sort of jumps into an ocean at no discernible point. (It covers scenegraphs I know, but why start there? Why not animation? Look for my own part two of programming a pong clone to animation and early concepts in game programming.)