Acquiring Reflectance and Shape from Continuous Spherical Harmonic Illumination
Borom Tunwattanapong    Graham Fyffe    Paul Graham    Jay Busch    Xueming Yu    Abhijeet Ghosh*    Paul Debevec   
USC Institute for Creative Technologies    Imperial College London*

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.

Left: Acquisition Setup    Middle: Reflectance Maps    Right: Rendered 3D Model

SIGGRAPH 2013 Paper
SpecularScanning.pdf, (20.2MB)
SH_Shape_Reflectance_SIGGRAPH2013.pdf, (20.2MB)

SIGGRAPH 2013 Paper
SH_Shape_Reflectance_SIGGRAPH2013.mp4, (52.3MB)

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