BRDF-Shop: creating physically correct bidirectional reflectance distribution functions

A majority of the artists in the graphics community use one of the mainstream packages for modeling and designing a scene for 3D rendering. These packages - such as Alias´ Maya, Discreet´s 3ds Max, or Newtek´s Lightwave -provide slider bars and numerical inputs that let the artist design the material´s attributes, such as smoothness and metallic qualities. While advanced users develop a mental mapping from numerical input to material appearance, novice users might not have a natural feel for a material´s numeric parameterization. We present a novel and intuitive approach for material design through direct control of the material´s bidirectional reflectance distribution function (BRDF) via a series of brush strokes. Using our system, BRDF-Shop, the artist can paint highlights onto a spherical canvas and model a physically correct BRDF. Our principal hypothesis behind this approach is that artists understand materials through the shape and position of the highlights. We propose that these brush strokes; in combination with a real-time display, allow the artist to create a BRDF with intrinsic knowledge of how the highlight will appear on a given object.