A lot of early 3D games had the problem where you'd be trundling merrily along and suddenly everything was black, with an island of what looked like the hollow facade shell of the scene you'd been walking through rising into the distance above. Because you'd fallen out of the world. I remember this being a particular and long-standing problem for Bethesda Softworks, though they certainly weren't alone. It's been a while since I've seen it in the wild, so it seems we've gotten past it. My question is two-part:
1) What was the cause, or causes, of this? (My guess is that it's to do with floating-point-precision related seams between polygons, interacting with point-modeled character position, i.e. floor chunk A ends at position 1.0, floor chunk B starts at position 0.9998 and for a microsecond your position is 0.99992, and boom, you fall through the world. But that's just a guess.)
2) How did it get fixed?