Okay, this was probably a little silly, but.. as a further test of the placement-driven terrain painting, I hooked up roads to create sand around them. Showed up a number of bugs, including some in my bounding boxes (vsBox2D and vsBox3D, for those keeping track at home), and in my octree code (vsOctree). Think I have those all fixed, now.
Still have a few minor glitches to sort out, such as roads not properly clearing the terrain under themselves when they’re moved or removed. It’s easy to do that naively, but the naive approach runs into problems when the roads are being removed because the map system is in the middle of shutting down, when you close the game. Needs a bit more work to make all of that happy.
But in general, am pleased with how this is turning out. It’s becoming surprisingly easy to make this sort of operation work with very little effort, now.