Direct Ray Tracing of Smoothed and Displacement Mapped Triangles

Brian Smits Peter Shirley Michael M. Stark

Abstract:

We present an algorithm for ray tracing displacement maps that requires no additional storage over the base model. Displacement maps are rarely used in ray tracing due to the cost associated with storing and intersecting the displaced geometry. This is unfortunate because displacement maps allow the addition of large amounts of geometric complexity into models. Our method works for models composed of triangles with normals at the vertices. In addition, we present a special purpose displacement that creates a smooth surface that interpolates the triangle vertices and normals. Thus two adjacent triangles which share two vertices and normals will be smoothly interpolated. This displacement can be added to the displacement associated with the object. The combination allows relatively coarse models to be displacement mapped and ray traced with much less storage and fewer artifacts due to tessellation.

Postscript and PDF versions of the paper are also available. A shortened version of this report was published at the Rendering Workshop in Brno, Czech Republic and is also online.