I wrote a similar program in plain Java + Swing (and no other libraries) years ago, which I dumped on GitHub here (there are a few screenshots): https://github.

I wrote a similar program in plain Java + Swing (and no other libraries) years ago, which I dumped on GitHub here (there are a few screenshots): https://github.com/idolize/ray-tracer https://github.com/idolize/ray-tracer