> A key insight is that sorting polygons correctly is inherently O(N^2), not O(N lg N) as most would initially assume. This is because polygon overlap is not a transitive property (A in front of B and B in front of C does NOT imply A in front of C, due to cyclic overlap.) This means you can't use O(N lg N) sorting, which in turn means sorting 1000 polygons requires a million comparisons -- infeasible for hardware at the time.

A key insight for binary space partitioning is that it also solves the problem above my making sure this never happens. It slices polygons for that specific reason.