Preview window that displays the results of live ray-tracing as you pass the mouse over the scene.
Screen shots can be saved to TIFF format.
gphoton excels is in the ray-tracing of reflective surfaces like spheres and cylinders.
The ray-tracing engine is capable of rendering many curved surfaces without using polygonic approximations, resulting in stunning multi-reflective output.
OpenGL scene approximation
RPM binaries available as well as source code.