Practical Multiple-Scattering Sheen Using Linearly Transformed Cosines

We introduce a new volumetric sheen BRDF that approximates scattering observed in surfaces covered with normally-oriented fibers. Our previous sheen model was motivated by measured cloth reflectance, but lacked significant backward scattering. The model presented here allows a more realistic cloth appearance and can also approximate a dusty appearance. Our sheen model is implemented using a linearly transformed cosine (LTC) lobe fitted to a volumetric scattering layer. We detail the fitting process, and present and discuss our results.