I had a fun experiment to see what kind of 3D engine I can write using Free software. I got to test out some interesting design approaches. You can download my source which uses the MIT license.

Check out my 3D engine code

You will need

OpenSceneGraph (OSG)
OpenAL
Lua
LuaBind
OpenDynamicsEngine (ODE)
Boost

I started on quick basic and my first game was a ascii based RPG. I moved on to develop a wireframe 3D editor in basic! This was all when I was in junior high. The most challenging programming I have done is 3D game engine development because it requires so many disciplines to be fused into this super awesome monster of an application. I focus on clean design using modern techniques. I think the future in game engine design is in concurrency. How can I make a game run on an 8 processor machine? Maybe a little bit of functional programming can help.