I vaguely remember reading a short story or novella, probably in the late 1980s or early 1990s, where, across the space of a couple of generations, something odd (affecting gravity maybe?) required that Earth be turned into a cube. Then, once kids had been born knowing only the cube-world, they had to reverse the process (so these kids perceived the horizon as being U-shaped, being accustomed to the edges of the cube).
That's pretty much all I remember. Any ideas?