Jason Lawrence

selected publications

1. SIGGRAPH

   GenBRDF: Discovering New Analytic BRDFs with Genetic Programming

   Brady, A., Lawrence, J., Peers, P., and Weimer, W.

   ACM Transactions on Graphics (Proc. of SIGGRAPH) 33(4), 2014.

   Abs BibTeX

   We present a framework for learning new analytic BRDF models through Genetic Programming that we call genBRDF. This approach to reflectance modeling can be seen as an extension of traditional methods that rely either on a phenomenological or empirical process. Our technique augments the human effort involved in deriving mathematical expressions that accurately characterize complex high-dimensional reflectance functions through a large-scale optimization. We present a number of analysis tools and data visualization techniques that are crucial to sifting through the large result sets produced by genBRDF in order to identify fruitful expressions. Additionally, we highlight several new models found by genBRDF that have not previously appeared in the BRDF literature. These new BRDF models are compact and more accurate than current state-of-the-art alternatives.

   @article{Brady2014,
     abbr = {SIGGRAPH},
     selected = true,
     author = {Brady, A. and Lawrence, J. and Peers, P. and Weimer, W.},
     title = {GenBRDF: Discovering New Analytic BRDFs with Genetic Programming},
     journal = {ACM Transactions on Graphics (Proc. of SIGGRAPH)},
     year = {2014},
     volume = {33},
     number = {4},
     issn = {0730-0301},
     html = {https://doi.org/10.1145/2601097.2601193}
   }
   

2. SIGGRAPH

   Genetic Programming for Shader Simplification

   Sitthi-Amorn, P., Modly, N., Weimer, W., and Lawrence, J.

   ACM Transactions on Graphics (Proc. of SIGGRAPH Asia) 30(6), 2011.

   Abs BibTeX

   We present a framework based on Genetic Programming (GP) for automatically simplifying procedural shaders. Our approach computes a series of increasingly simplified shaders that expose the inherent trade-off between speed and accuracy. Compared to existing automatic methods for pixel shader simplification [Olano et al. 2003; Pellacini 2005], our approach considers a wider space of code transformations and produces faster and more faithful results. We further demonstrate how our cost function can be rapidly evaluated using graphics hardware, which allows tens of thousands of shader variants to be considered during the optimization process. Our approach is also applicable to multi-pass shaders and perceptual-based error metrics.

   @article{Sitthiamorn2011,
     abbr = {SIGGRAPH},
     selected = true,
     author = {Sitthi-Amorn, P. and Modly, N. and Weimer, W. and Lawrence, J.},
     title = {Genetic Programming for Shader Simplification},
     journal = {ACM Transactions on Graphics (Proc. of SIGGRAPH Asia)},
     year = {2011},
     volume = {30},
     number = {6},
     html = {https://doi.org/10.1145/2070781.2024186}
   }
   

3. SIGGRAPH

   A Coaxial Optical Scanner for Synchronous Acquisition of 3D Geometry and Surface Reflectance

   Holroyd, M., Lawrence, J., and Zickler, T.

   ACM Transactions on Graphics (Proc. of SIGGRAPH) 29(4), 2010.

   Abs Supp BibTeX

   We present a novel optical setup and processing pipeline for measuring the 3D geometry and spatially-varying surface reflectance of physical objects. Central to our design is a digital camera and a high frequency spatially-modulated light source aligned to share a common focal point and optical axis. Pairs of such devices allow capturing a sequence of images from which precise measurements of geometry and reflectance can be recovered. Our approach is enabled by two technical contributions: a new active multiview stereo algorithm and an analysis of light descattering that has important implications for image-based reflectometry. We show that the geometry measured by our scanner is accurate to within 50 microns at a resolution of roughly 200 microns and that the reflectance agrees with reference data to within 5.5%. Additionally, we present an image relighting application and show renderings that agree very well with reference images at light and view positions far from those that were initially measured.

   @article{Holroyd2010,
     abbr = {SIGGRAPH},
     selected = true,
     author = {Holroyd, M. and Lawrence, J. and Zickler, T.},
     title = {A Coaxial Optical Scanner for Synchronous Acquisition of 3D Geometry and Surface Reflectance},
     journal = {ACM Transactions on Graphics (Proc. of SIGGRAPH)},
     year = {2010},
     month = jul,
     volume = {29},
     number = {4},
     html = {https://doi.org/10.1145/1778765.1778836},
     supp = {coaxial_analysis.pdf}
   }
   

4. SIGGRAPH

   Inverse Shade Trees for Non-Parametric Material Representation and Editing

   Lawrence, J., Ben-Artzi, A., DeCoro, C., Matusik, W., Pfister, H., Ramamoorthi, R., and Rusinkiewicz, S.

   ACM Transactions on Graphics (Proc. of SIGGRAPH) 25(3), 2006.

   Abs BibTeX

   Recent progress in the measurement of surface reflectance has created a demand for non-parametric appearance representations that are accurate, compact, and easy to use for rendering. Another crucial goal, which has so far received little attention, is editability: for practical use, we must be able to change both the directional and spatial behavior of surface reflectance (e.g., making one material shinier, another more anisotropic, and changing the spatial "texture maps" indicating where each material appears). We introduce an Inverse Shade Tree framework that provides a general approach to estimating the "leaves" of a user-specified shade tree from high-dimensional measured datasets of appearance. These leaves are sampled 1- and 2-dimensional functions that capture both the directional behavior of individual materials and their spatial mixing patterns. In order to compute these shade trees automatically, we map the problem to matrix factorization and introduce a flexible new algorithm that allows for constraints such as non-negativity, sparsity, and energy conservation. Although we cannot infer every type of shade tree, we demonstrate the ability to reduce multi-gigabyte measured datasets of the Spatially-Varying Bidirectional Reflectance Distribution Function (SVBRDF) into a compact representation that may be edited in real time.

   @article{Lawrence2006,
     abbr = {SIGGRAPH},
     selected = {true},
     author = {Lawrence, J. and Ben-Artzi, A. and DeCoro, C. and Matusik, W. and Pfister, H. and Ramamoorthi, R. and Rusinkiewicz, S.},
     title = {Inverse Shade Trees for Non-Parametric Material Representation and Editing},
     journal = {ACM Transactions on Graphics (Proc. of SIGGRAPH)},
     year = {2006},
     volume = {25},
     number = {3},
     html = {https://doi.org/10.1145/1141911.1141949}
   }