Incredibly detailed series of 10 articles by the inimitable Jacco Bikker about efficient ray tracing. Don’t be fooled by the title “How to build a BVH,” it also lays out data structures for textured triangles and much else for making a modern ray tracer, finishing up with using OpenCL (!) to ray trace on the GPU. Tip: for the code, build and run each project separately in VS 2019, or you’ll get “cannot open program database” compilation errors. Also, WASD+FR (which, oddly, the program receives and responds to even while I’m typing in this window) and numpad for rotation.
Three.js path tracer. Sure, I prefer dedicated hardware to accelerate ray tracing, but this site presents a wide-ranging effort. The sheer number of different browser programs offered, all just a click away, is great. I’ve checked out only a handful so far, such as the quadric shape explorer (pro tip: WASD+QZ for moving around). Bonus: the README page includes rare photos of Arthur Appel, the first person to publish anything about ray tracing, back in 1968.
You can render a sphere nicely without ray tracing, but it’s certainly more work and with quite a few challenges to overcome. Ben Golus has an extremely in-depth article about techniques for doing so in Unity.
Origami Simulator in WebGL for the browser, from MIT. Won’t teach you how to fold – all folds happen at once – but it’s fun to look through the patterns.
The Reverse Phi Illusion is so impressive. There is movement between frames, but it repeats. Play with the controls to see what’s going on frame-wise.