Certainly. Have a look here: https://github.com/peterkutz/GPUPathTracer. It's a physically based path tracer, I it uses a kd-tree but I am not sure if they actually got around to implementing it. Well, actually, CUDA already has kd-tree code (cukd). There's also tokaspt, which is a CUDA port of the "smallpt" program. An OpenCL port also exists, but has less features.

As for whitted ray tracing, though, I don't know of any, but that's probably because I don't look around for that. You should be able to modify the code to a whitted model fairly easily, though, the hardest part in a ray tracer is getting the initialization logic and various subsystems (ray-scene intersection, asset loading) up, the actual rendering code is very simple.

Plus, why would you implement whitted ray tracing on a GPU when rasterization can achieve pretty much the same visual results much faster? I believe that is why people prefer to implement realistic rendering methods on the GPU, rather than basic ray tracing, but there have been whitted benchmarks published so there must be some code somewhere.

Also, welcome to GameDev!

Yeah, ray tracing is so demanding that I never use it in my work. It simply is not needed for a game with the alternatives.

Someday, maybe within 10 to 20 years, computer power will allow significant ray tracing in any game with all the other assets, but until then it is relegated to image rendering for the most part.

Master shader technology and you will forget about ray tracing. Usually you would get more real life, realistic appearance with shaders anyhow.

Master shader technology and you will forget about ray tracing. Usually you would get more real life, realistic appearance with shaders anyhow.

It might surprise you just how many shaders implement mini-raytracers internally, or use raytracing techniques...

There are plenty of hybrid technologies out there, but fact is that raytracing is demanding on performance.