GJK
A model tetrahedron I built out of Q-tips in order to wrap my brain around the geometry. Not pictured: folded post-it notes playing the part of Voronoi boundaries.
A long (long) time ago I made two big posts going through the GJK algorithm, how it works, and how to implement it efficiently. They were pretty cool and even had interactive diagrams in them designed to illustrate the geometric concepts and help to intuitively communicate why things work the way they do.
...And then my hosting provider got hacked and my website got wrecked.
...And then it turned out that my backups had failed to capture the core dependency that the diagrams relied on.
...And then it turned out that the dependency had died a sad, sad death. And I never found the time to fix that.
...And then later my hosting provider decided to get rid of me altogether (fun! - not) and this whole site kind of died. And since it was a major pain to get it up and running again in a new format on new hosting, well, the GJK pages have been gone from the internet for quite some time.
Anyways, they're fixed now. I think. (I hope.) There might be some errors that crept in during the migration from their original incarnation to where they live now. And maybe I messed things up when I cleaned up the prose. So ...they're probably not perfect, but they are back. And so are the interactive diagrams! I had to write some Javascript for the first time in forever and learn how to work with HTML <canvas> elements, but they've all been rewritten and they work. Probably. At least in Firefox.
I'll probably be messig with the pages and tweaking them as I find issues, but perfect or not, here they are: