overview of ray tracing

An overview of ray tracing is available at a siggraph web site. I'm looking into it as a way to learn some 3-d graphics math by applying it in a simple program. Unfortunately I'm expecting the images produced by such a simple program not to be very interesting.

The pictures at this site about terrain generation with ray marching do look interesting though, and the author claims that the code is simple as well. Also, the explanation of the method involves techniques similar to ray tracing.