Per-pixel displacement mapping with distance functions

In this chapter, we present distance mapping, a technique for adding small-scale dis-placement mapping to objects in a pixel shader. We treat displacement mapping as a ray-tracing problem, beginning with texture coordinates on the base surface and calcu-lating texture coordinates where the viewing ray intersects the displaced surface. For this purpose, we precompute a three-dimensional distance map, which gives a measure of the distance between points in space and the displaced surface. This distance map gives us all the information necessary to quickly intersect a ray with the surface. Our algorithm significantly increases the perceived geometric complexity of a scene while maintaining real-time performance. Cook (1984) introduced displacement mapping as a method for adding small-scale detail to surfaces. Unlike bump mapping, which affects only the shading of surfaces, displacement mapping adjusts the positions of surface elements. This leads to effects not possible with bump mapping, such as surface features that occlude each other an