OctreeBTFs – A compact, seamless and distortion-free reflectance representation

In: Computers & Graphics (Nov. 2017), 68(21-31)
 

Abstract

Conventional reflectance acquisition techniques rely on the reconstruction of a closed surface geometry and a subsequent surface parametrization that is required to store the reflectance data parametrized over the surface. Among the main drawbacks of this approach is the need for a suitable surface parametriza- tion which is particularly challenging for inaccuracies in the reconstruction or holes occurring due to missing observations. An inappropriate parametrization, in turn, leads to artifacts such as distortion ef- fects and visible seams which severely decrease the visual quality of the digitized object appearance. Furthermore, standard reflectance representations are either compact and less expressive or not compact and expressive. In this paper, we introduce a compact, accurate, seamless and distortion-free volumetric reflectance representation to address these issues. This novel representation named OctreeBTFs is based on storing surface reflectance in terms of Apparent BRDFs in a grid structure that is adapted to the un- derlying object geometry. The local coordinate systems required to store and render the local reflectance behavior of anisotropic surface reflectance characteristics are computed based on a novel, biologically in- spired local approach, instead of computing them based on the texture coordinates obtained from the uv-parameterization. The resulting octree-based data structure results in a more compact BTF represen- tation that can be rendered in real-time with multiple light sources. Finally, our data structure can also be applied to other reflectance representations or to store other information such as physical properties.

Keywords: bidirectional texture function, Object digitization, real-time rendering, Spatially varying reflectance, Tangent field computation

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Bibtex

@ARTICLE{krumpen-2017-OctreeBTFs,
    author = {Krumpen, Stefan and Weinmann, Michael and Klein, Reinhard},
     pages = {21--31},
     title = {OctreeBTFs – A compact, seamless and distortion-free reflectance representation},
   journal = {Computers {\&} Graphics},
    volume = {68},
      year = {2017},
     month = nov,
  keywords = {bidirectional texture function, Object digitization, real-time rendering, Spatially varying
              reflectance, Tangent field computation},
  abstract = {Conventional reflectance acquisition techniques rely on the reconstruction of a closed surface
              geometry and a  subsequent surface parametrization that is required to store the reflectance data
              parametrized over the surface. Among the main drawbacks of this approach is the need for a suitable
              surface parametriza- tion which is particularly challenging for inaccuracies in the reconstruction
              or holes occurring due to missing observations. An inappropriate parametrization, in turn, leads to
              artifacts such as distortion ef- fects and visible seams which severely decrease the visual quality
              of the digitized object appearance. Furthermore, standard reflectance representations are either
              compact and less expressive or not compact and expressive. In this paper, we introduce a compact,
              accurate, seamless and distortion-free volumetric reflectance representation to address these
              issues. This novel representation named OctreeBTFs is based on storing surface reflectance in terms
              of Apparent BRDFs in a grid structure that is adapted to the un- derlying object geometry. The local
              coordinate systems required to store and render the local reflectance behavior of anisotropic
              surface reflectance characteristics are computed based on a novel, biologically in- spired local
              approach, instead of computing them based on the texture coordinates obtained from the
              uv-parameterization. The resulting octree-based data structure results in a more compact BTF
              represen- tation that can be rendered in real-time with multiple light sources. Finally, our data
              structure can also be applied to other reflectance representations or to store other information
              such as physical properties.},
       doi = {https://doi.org/10.1016/j.cag.2017.08.001}
}