Authors
Borom Tunwattanapong, Graham Fyffe, Paul Graham, Jay Busch, Xueming Yu, Abhijeet Ghosh, Paul Debevec
USC Institute for Creative Technologies; Imperial College London
Portals
Abstract
We present a novel technique for acquiring the geometry and spatially-varying reflectance properties of 3D objects by observing them under continuous spherical harmonic illumination conditions. The technique is general enough to characterize either entirely specular or entirely diffuse materials, or any varying combination across the surface of the object. We employ a novel computational illumination setup consisting of a rotating arc of controllable LEDs which sweep out programmable spheres of incident illumination during 1-second exposures. We illuminate the object with a succession of spherical harmonic illumination conditions, as well as photographed environmental lighting for validation. From the response of the object to the harmonics, we can separate diffuse and specular reflections, estimate world-space diffuse and specular normals, and compute anisotropic roughness parameters for each view of the object. We then use the maps of both diffuse and specular reflectance to form correspondences in a multiview stereo algorithm, which allows even highly specular surfaces to be corresponded across views. The algorithm yields a complete 3D model and a set of merged reflectance maps. We use this technique to digitize the shape and reflectance of a variety of objects difficult to acquire with other techniques and present validation renderings which match well to photographs in similar lighting.
Contribution
- A novel computational illumination system for illuminating an object with high-resolution continuous spherical lighting conditions.
- The use of spherical harmonic illumination conditions for diffuse and specular reflectance component separation.
- A method of using higher-order spherical harmonics to measure the albedo, reflection vector, roughness, and anisotropy parameters of a specular reflectance lobe.
- A multi-view stereo algorithm which uses both diffuse and specular albedo and surface orienta
Related Works
Spatially Varying BRDF Capture; Using Extended Light Sources; Reflectance from Spherical Illumination; Geometry from Specular Reflection