Time-varying BRDFs.

The properties of virtually all real-world materials change with time, causing their bidirectional reflectance distribution functions (BRDFs) to be time varying. However, none of the existing BRDF models and databases take time variation into consideration; they represent the appearance of a material at a single time instance. In this paper, we address the acquisition, analysis, modeling, and rendering of a wide range of time-varying BRDFs (TVBRDFs). We have developed an acquisition system that is capable of sampling a material's BRDF at multiple time instances, with each time sample acquired within 36 sec. We have used this acquisition system to measure the BRDFs of a wide range of time-varying phenomena, which include the drying of various types of paints (watercolor, spray, and oil), the drying of wet rough surfaces (cement, plaster, and fabrics), the accumulation of dusts (household and joint compound) on surfaces, and the melting of materials (chocolate). Analytic BRDF functions are fit to these measurements and the model parameters' variations with time are analyzed. Each category exhibits interesting and sometimes nonintuitive parameter trends. These parameter trends are then used to develop analytic TVBRDF models. The analytic TVBRDF models enable us to apply effects such as paint drying and dust accumulation to arbitrary surfaces and novel materials.

[1]  Jim X. Chen,et al.  Integrating physics-based computing and visualization: modeling dust behavior , 1999, Comput. Sci. Eng..

[2]  Alan Edelman,et al.  Modeling and rendering of weathered stone , 1999, SIGGRAPH.

[3]  Chen Xu,et al.  Synthesis of Material Drying History: Phenomenon Modeling, Transferring and Rendering , 2005, NPH.

[4]  Julie Dorsey,et al.  Rendering of Wet Materials , 1999, Rendering Techniques.

[5]  Gary W. Meyer,et al.  Modeling pigmented materials for realistic image synthesis , 1992, TOGS.

[6]  David Salesin,et al.  Computer-generated watercolor , 1997, SIGGRAPH.

[7]  Wojciech Matusik,et al.  A data-driven reflectance model , 2003, ACM Trans. Graph..

[8]  Shree K. Nayar,et al.  Time-varying surface appearance: acquisition, modeling and rendering , 2006, ACM Trans. Graph..

[9]  H. Shum,et al.  Appearance manifolds for modeling time-variant appearance of materials , 2006, SIGGRAPH 2006.

[10]  Michael C. Dorf,et al.  Why some things are darker when wet. , 1988, Applied optics.

[11]  Takashi Okamoto,et al.  A lighting model aiming at drive simulators , 1990, SIGGRAPH.

[12]  Siu Chi Hsu,et al.  Simulating dust accumulation , 1995, IEEE Computer Graphics and Applications.

[13]  Shree K. Nayar,et al.  Generalization of Lambert's reflectance model , 1994, SIGGRAPH.

[14]  Niels da Vitoria Lobo,et al.  Determining wet surfaces from dry , 1995, Proceedings of IEEE International Conference on Computer Vision.

[15]  Joe DeMaio,et al.  Introduction to Color , 1997 .

[16]  Stephen H. Westin,et al.  Image-based bidirectional reflectance distribution function measurement. , 2000, Applied optics.

[17]  Chen Xu,et al.  Synthesis of material drying history: phenomenon modeling, transferring and rendering , 2005, NPH.

[18]  Bo Sun,et al.  Time-Varying BRDFs , 2006, NPH.

[19]  Gregory J. Ward,et al.  Measuring and modeling anisotropic reflection , 1992, SIGGRAPH.

[20]  P. Belhumeur,et al.  Capture, analysis and synthesis of textured surfaces with variation in illumination, viewpoint, and time , 2004 .

[21]  D. Marquardt.  An Algorithm for Least-Squares Estimation of Nonlinear Parameters , 1963 .

[22]  Pat Hanrahan,et al.  Modeling and rendering of metallic patinas , 1996, SIGGRAPH.

[23]  Norman I. Badler,et al.  Imperfection for realistic image synthesis , 1990, Comput. Animat. Virtual Worlds.

[24]  Pat Hanrahan,et al.  Flow and changes in appearance , 2006, SIGGRAPH Courses.

[25]  Shree K. Nayar,et al.  Time-varying textures: definition, acquisition, and synthesis , 2005, SIGGRAPH '05.

[26]  K. Torrance,et al.  Theory for off-specular reflection from roughened surfaces , 1967 .

[27]  Jim X. Chen,et al.  Real-time simulation of dust behavior generated by a fast traveling vehicle , 1999, TOMC.

[28]  James F. Blinn,et al.  Light reflection functions for simulation of clouds and dusty surfaces , 1982, SIGGRAPH.

[29]  Shree K. Nayar,et al.  Reflectance and texture of real-world surfaces , 1999, TOGS.

[30]  Steve Marschner,et al.  Image-Based BRDF Measurement Including Human Skin , 1999, Rendering Techniques.