(a) Our optimized lighting emphasizes materials (b) Poor lighting de-emphasizes materials Figure 1: Our method (a) automatically optimizes the lighting to enhance material-specific visual features. The lighting reveals the thin and thick parts of the subsurface scattering wax candle, it accentuates the Fresnel reflections along the side of the porcelain vase and it adds strong specular highlights to emphasize the shiny chrome metal of the sculpture. Poorly designed lighting (b) diminishes these characteristic visual features of the materials. The candle appears more like solid plastic, the vase appears to be made of diffuse clay and the sculpture no longer looks like it is made of chrome. This technical report is an extended version of our EGSR 2011 paper. 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.
In the context of photorealistic rendering, REF take inspiration from lighting design practice to generate environment maps that enhance material depiction.
Optimizing environment maps for material depiction
In CGF, Eurographics Association, EGSR’11
Computer Science