Adaptive sampling of reflectance fields

Image-based relighting achieves high quality in rendering, but it requires a large number of measurements of the reflectance field. This article discusses sampling techniques that improve on the trade-offs between measurement effort and reconstruction quality. Specifically, we (i) demonstrate that sampling with point lights and from a sparse set of incoming light directions creates artifacts which can be reduced significantly by employing extended light sources for sampling, (ii) propose a sampling algorithm which incrementally chooses light directions adapted to the properties of the reflectance field being measured, thus capturing significant features faster than fixed-pattern sampling, and (iii) combine reflectance fields from two different light domain resolutions. We present an automated measurement setup for well-defined angular distributions of the incident, indirect illumination. It is based on programmable spotlights with controlled aperture that illuminate the walls around the scene.