Displacement mapping is the process of displacing vertices (usually created via the process of tessellation) based upon the information sampled from a height map texture. This process extends upon traditional normal mapping to provide additional detail to the surface. Displacement mapping is not a replacement for normal mapping. They both work together to produce a more realistic result. While normal mapping manipulates lighting to give the appearance of a more irregular surface, displacement mapping will physically manipulate the mesh to give it additional 3D detail—especially noticeable for silhouettes, contours, and therefore shadows. The example output shown in Adding surface detail with normal mapping highlights the impact of normal and displacement mapping both separately and when combined.

In this chapter, we will learn how to use these techniques together to produce more realistic real-time rendering results, and then see how to extend the process to implement local deformations such as footprints or scratch marks.