I've returned to work on my lunar lander program by spending some time on the planet generation code. It now collects closed polygons and then throws out any that have negative area, so there are no longer any inaccessible interior regions:
I lost a fair amount of code in doing this. There is no longer a BSP representation; I'll need to do that in a different way if I end up needing it. There's also not a triangulation yet either, but I have code lying around that I should be able to plug in for that.
The current top priority is coming up with landing targets. I've been trying to think of a good way to identify accessible landing targets on a random terrain like this. Ideally it would be able to find "interesting" places to land.