Optimizing Environment Maps for Material Depiction
We present an automated system for optimizing and synthesizing environment maps that enhance the appearance of materials in a scene. We first identify a set of lighting design principles for material depiction. Each principle specifies the distinctive visual features of a material and describes how environment maps can emphasize those features. We express these principles as linear or quadratic image quality metrics, and present a general optimization framework to solve for the environment map that maximizes these metrics. We accelerate metric evaluation using an approach dual to precomputed radiance transfer (PRT). In contrast to standard PRT that integrates light transport over the lighting domain to generate an image, we pre-integrate light transport over the image domain to optimize for lighting. Finally we present two techniques for transforming existing photographic environment maps to better emphasize materials. We demonstrate the effectiveness of our approach by generating environment maps that enhance the depiction of a variety of materials including glass, metal, plastic, marble and velvet.