Displacement mapping

Displacement mapping is an alternative computer graphics technique in contrast to bump, normal, and parallax mapping, using a texture or height map to cause an effect where the actual geometric position of points over the textured surface are displaced, often along the local surface normal, according to the value the texture function evaluates to at each point on the surface. It gives surfaces a great sense of depth and detail, permitting in particular self-occlusion, self-shadowing and silhouettes; on the other hand, it is the most costly of this class of techniques owing to the large amount of additional geometry.

For years, displacement mapping was a peculiarity of high-end rendering systems like PhotoRealistic RenderMan, while realtime APIs, like OpenGL and DirectX, were only starting to use this feature. One of the reasons for this is that the original implementation of displacement mapping required an adaptive tessellation of the surface in order to obtain enough micropolygons whose size matched the size of a pixel on the screen.