Tokaspt, an excellent real-time path tracing app

Just stumbled upon this very impressive CUDA based path tracer: http://code.google.com/p/tokaspt/ for exe and source (The app itself has been available since January 2009)

Although the scenes are quite simple (spheres and planes only), it's extremely fast and it converges literally in a matter of milliseconds to a high quality image. Navigation is as close to real-time as it gets. There are 4 different scenes to choose from (load scene with F9) and they can be modified at will: parameters are sphere size, color, emitting properties, 3 material BRDFs (diffuse (matte), specular (mirror) and refractive (glass)) and sphere position. Path trace depth and spppp (samples per pixel per pass) can also be altered on the fly thanks to the very convenient GUI with sliders. When moving around and ghosting artefacts appear, press the "reset acc" button to clear the accumulation buffer and get a clean image. Definitely worth messing around with!