. This models a sphere with a bumpy surface with the result that both its outline and its shadow are rendered realistically. Bump mapping is a technique in
computer graphics to make a
rendered surface look more realistic by simulating small displacements of the surface. However, unlike
displacement mapping, the surface geometry is not modified. Instead only the surface normal is modified as if the surface had been displaced. The modified surface normal is then used for lighting calculations (using, for example, the
Phong reflection model) giving the appearance of detail instead of a smooth surface. Bump mapping is much faster and consumes fewer resources for the same level of detail compared to displacement mapping because the geometry remains unchanged. There are also extensions which modify other surface features in addition to increasing the sense of depth.
Parallax mapping and
horizon mapping are two such extensions. The primary limitation with bump mapping is that it perturbs only the surface normals without changing the underlying surface itself. Silhouettes and shadows therefore remain unaffected, which is especially noticeable for larger simulated displacements. This limitation can be overcome by techniques including displacement mapping where bumps are applied to the surface or using an
isosurface.
Methods There are two primary methods to perform bump mapping. The first uses a
height map for simulating the surface displacement yielding the modified normal. This is the method invented by Blinn ==Realtime bump mapping techniques==