Bump mapping

Bump mapping is a computer graphics technique where at each pixel, a perturbation to the surface normal of the object being rendered is looked up in a texture map and applied before the illumination calculation is done (see, for instance, Phong shading). The result is a richer, more detailed surface representation that more closely resembles the details inherent in the natural world.

The difference between displacement mapping and bump mapping is evident in this image; in bump mapping, the normal alone is perturbed, not the geometry itself. This leads to artifacts in the silhoutte of the object (the sphere still has a circular silhoutte).