  Existing bidirectional reflectance distribution function (BRDF) models are
capable of capturing the distinctive highlights produced by the fibrous nature
of wood. However, capturing parameter textures for even a single specimen
remains a laborious process requiring specialized equipment. In this paper we
take a procedural approach to generating parameters for the wood BSDF. We
characterize the elements of trees that are important for the appearance of
wood, discuss techniques appropriate for representing those features, and
present a complete procedural wood shader capable of reproducing the growth
patterns responsible for the distinctive appearance of highly prized
``figured'' wood. Our procedural wood shader is random-access, 3D, modular, and
is fast enough to generate a preview for design.
