A BRDF postprocess to integrate porosity on rendered surfaces

摘要

The behavior of light interacting with materials is a crucialnfactor in achieving a high degree of realism in image synthesis. Localnillumination processes, describing the interactions between a point ofnthe surface and a shading ray, are evaluated by bidirectionalnreflectance distribution functions (BRDFs). Current theoretical BRDFsnuse surface models restricted to roughness only, sometimes at differentnscales. We present a more complete surface micro-geometry description,nsuitable for some common surface defects, including porosity andnmicro-cracks; both of them are crucial surface features since theynstrongly influence light reflection properties. These new features arenmodeled by holes inserted in the surface profile, depending on twonparameters: the proportion of surface covered by the defects and thenmean geometric characteristic of these defects. In order to preserve thenadvantages and characteristics of existing BRDFs, a postprocessingnmethod is adopted (we integrate our technique into existing models,ninstead of defining a completely new one). Beyond providing graphicalnresults closely matching real behaviors, this method moreover opens thenway to various important new considerations in computer graphics (fornexample, changes of appearance due to the degree of humidity)