A bump map is a little different and slightly less effective than a normal map. A normal map uses values of red, green and blue to denote slope components along three directions spread 120º apart. a bump map is essentially just a greyscale map showing displacement relative to the basic surface of the model object. These both merely alter the texture of the surface by adding the appearance of variations in light and shadow. A displacement map is similar to the terrain maps in Bryce, it actually alters the geometry of the object by displacing points in the surface through space. Bryce lacks normal mapping and, except for terrain and symmetry objects, displacement. I'm not sure if 7 has added to either of these capabilities.