[starwed]

It's still the case that if you're sufficiently far away from a nonspherical object, it'll effectively act like a point source.

I'd guess this is what the OP was recalling.

[bzbarsky]

Well, sure. If you're far enough away it _looks_ like a point source!

That doesn't apply to being on the face of a cube, though; that's not nearly far enough away, obviously. :)