CrazyBump Shape Recognition
Based on the article, it seems like, when it adds &quot;directional lighting information&quot;, the program tries to infer a location of a light source and base the normals on the colors with the added information of the directional lighting from the pixel to the inferred light source. I feel like I'm making no sense right now, so here's an example using their pictures:


As you can see, on the far right of the normal map, it's very pink, just like how the sample image is completely white. I would assume this is the case because the inferred light is directly on top of it, with all the normals (in sort of a curved fashion, resulting in the gradient) pointing right at it. In contrast...

This normal map isn't trying to figure out a light source, and instead just kind of uses the sample texture as a heightmap of sorts.
Late reply, but hope this helps! :)