A physically-based BRDF model for retroreflection.

We introduce an analytical BRDF model tailored to the realistic rendering of retroreflective materials. Though these specially-designed materials are frequently encountered in our daily life, such as high-visibility clothing and traffic signs, their reflectance behaviors are barely analyzed and simulated in a physically meaningful manner in computer graphics. To understand how retroreflection is actually generate, we conduct a detailed optical analysis on a typical prismatic sheet which is the most widely used retroreflector in the material industry. In particular, the effective retroreflective area of the sheet is studied theoretically and experimentally. Based on the study, we derive a practical BRDF model that takes into account all types of reflection from the sheet, including mirror reflection, retroreflection, and diffuse reflection. Experiments confirm that our BRDF can produce visually pleasing rendered images with high fidelity retroreflection effects which closely match those generated by the prismatic sheet.