Saint... I have an idea. Remember when I asked if the world map was done with an elevation map? What if I'm right? Fice brought up that such a map would be huge, and have to be highly detailed. That's very true... But I think we're forgetting something that FF7 takes full advantage of all the time; Vector colors/maps.
What if the elevation map is stored in the mesh itself as a vector map of some kind? You get detail for every point of the mesh, at very low overhead. Sending the vector map through a process to deform it before applying it to the mesh would make it easy to make it look like the world bends, and flattens.
Is this just a crazy I had, or could this be how they did it? Cause I really need to get my hands on that world mesh...