I have implemented a recursive ray tracer that uses a phong illumination model with multiple lights sources, distance attenuation, refractions, and shadows. The antialiasing method used is stochastic supersampling from a 2D Normal distribution. In order to speed things up I used a k-d Tree as an acceleration data structure as well as OpenMP for multi-threading, note you may need to enable OpenMP in Visual Studio to take advantage of multiple cores.
Inorder to compile the code you first need to unzip the fltk-1.3.3.7z file into the root of the project. Then open the ray.sln file and make the project. There is a preexisting ray.exe file in the Release folder that you can use, it may or may not work for you with out compiling the project.
Here are some example of scenes rendered by the raytracer
