So instead I read and relaxed some and also played with ray tracing a bit. I just felt like it, and also wanted to see if my maths was still up to it. And although I've lost most of it since my year in college, at least the basic 1% linear algebra I needed is still there.
You notice just how much anti-aliasing does to an image...
Sometimes it's fun to just play, without any purpose. But of course it would also be nice to put it to work, even though it's only 300 lines of code. I have no clue what I'd use it for though, so it probably will stay in my digital drawer for the rest of my life.