Modeling Anisotropic Surface Reflectance with Example-Based Microfacet Synthesis

ACM SIGGRAPH 2008 (to appear)

Abstract

      We present a new technique for the visual modeling of spatiallyvarying anisotropic reflectance using data captured from a single view. Reflectance is represented using a microfacet-based BRDF which tabulates the facets' normal distribution (NDF) as a function of surface location. Data from a single view provides a 2D slice of the 4D BRDF at each surface point from which we fit a partial NDF. The fitted NDF is partial because the single view direction coupled with the set of light directions covers only a portion of the "half-angle" hemisphere. We complete the NDF at each point by applying a novel variant of texture synthesis using similar, overlapping partial NDFs from other points. Our similarity measure allows azimuthal rotation of partial NDFs, under the assumption that reflectance is spatially redundant but the local frame may be arbitrarily oriented. Our system includes a simple acquisition device that collects images over a 2D set of light directions by scanning a linear array of LEDs over a flat sample. Results demonstrate that our approach preserves spatial and directional BRDF details and generates a visually compelling match to measured materials.

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Acknowledgements

The LED array was designed and produced by Le Ma. Qiang Dai helped us to capture the raw data. The authors thank Steve Lin for discussions on BRDF modeling and for proofreading this paper, and Dong Xu for discussions on NDF clustering. We also thank the anonymous reviewers for their helpful suggestions and comments.

BibTex reference

@article{Wang08,
    author = {Jiaping Wang and Shuang Zhao and Xin Tong and John Snyder and Baining Guo},
    title = {Modeling Anisotropic Surface Reflectance with Example-based Microfacet Synthesis},
    journal = {ACM Trans. Graph. (to appear in SIGGRAPH 2008)},
    volume = {??},
    number = {?},
    year = {2008},
    pages = {???--???},
    publisher = {ACM},
    address = {New York, NY, USA}
}