Surface
Mapping HyperGraph Table
of Contents. 
HyperGraph Home
page. We detect bumps in a surface by the relative darkness or lightness of thevsurface feature. In local illumination models, this is primarily determned by the direct diffuse reflection term which is proportional to N*L. N is the surface normal and L is the light vector. By modifying N, we can create spots of darkness or brightness.
James Blinn invented the method of perturbing the surface normal, N, by a "wrinkle" function. This changes the light interaction but not the actual size of the objects so that bump mapped objects appear smooth at the silhouette.
A Pixar Shutterbug image with texture and bump mapping. Notice that the surfaces appear to have bumps or gouges but that the silhouette of the object is still smooth.
Surface
Mapping
HyperGraph Table
of Contents.
HyperGraph Home
page.