THE SHAPE OF THE SPECULAR PEAK OF ROUGH SURFACES

The BRDF model developed by Torrance and Sparrow describes the specular reflection of rough surfaces. We compared this model to BRDF measurements of 4 man-made surfaces with very different roughnesses. We found that the azimuthal width of the specular peak decreases strongly with increasing illumination zenith angle, in the data as well as in the model. We furthermore propose a simplification of the model by dropping one of the assumptions on the surface structure. This simplification is equivalent to ignoring masking and shadowing effects, but alters the resulting BRDF in most cases only negligibly, and provides several advantages like easier implementation and faster computing time.