Quote - When you say "not from a grayscale image", now the words are being twisted. Forget the term grayscale image. Instead, think "topology delta matrix". Given a topology delta matrix, i.e. the difference between two meshes as measured along the surface normal vector from one to the other, you end up with exactly the data found in a bump map.

See what I mean? From that, you can construct all the normals.

Yeah, you know what Bill?
After I posted the few comments above and started planning how I could go about illustrating what I meant, I went back and re-read what you had written. I did that because I thought to myself there's no way BB is going to give such a simplistic answer and expect it to be taken as fact. So I figured something was up. ;-)
I realized I had read it wrong and I now see what you meant. Sorry about that, I didn't mean to take you out of context. I should have edited my reply, but I was already involved in something else. Got a nice fresh bottle of Jack Daniels here too. ;-)