Time: 39:45
It’s actually not all that difficult, it’s just straight parallax mapping, doing depth intersection tests against two depth maps. Hammersley is used to dither the slices, I don’t know why hammersley specifically was chosen though.
What I find much more confusing about it is how on earth they got the built-in interior cubemapping function to work with non-cube rooms. That whole node is black magic to me, I can’t tell what the hell it is doing, and of course… it’s not explained here.