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350
Reflection from Layered Surfaces due to Subsurface Scattering
, 1993
"... The reflection of light from most materials consists of two major terms: the specular and the diffuse. Specular reflection may be modeled from first principles by considering a rough surface consisting of perfect reflectors, or microfacets. Diffuse reflection is generally considered to result from ..."
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Cited by 233 (4 self)
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The reflection of light from most materials consists of two major terms: the specular and the diffuse. Specular reflection may be modeled from first principles by considering a rough surface consisting of perfect reflectors, or microfacets. Diffuse reflection is generally considered to result from multiple scattering either from a rough surface or from within a layer near the surface. Accounting for diffuse reflection by Lambert's Cosine Law, as is universally done in computer graphics, is not a physical theory based on first principles. This paper presents
Generalization of the Lambertian Model and Implications for Machine Vision
, 1992
"... Lambert's model for diffuse reflection is extensively used in computational vision. It is used explicitly by methods such as shape from shading and photometric stereo, and implicitly by methods such as binocular stereo and motion detection. For several realworld objects, the Lambertian model ca ..."
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Cited by 145 (12 self)
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Lambert's model for diffuse reflection is extensively used in computational vision. It is used explicitly by methods such as shape from shading and photometric stereo, and implicitly by methods such as binocular stereo and motion detection. For several realworld objects, the Lambertian model can prove to be a very inaccurate approximation to the diffuse component. While the brightness of a Lambertian surface is independent of viewing direction, the brightness of a rough diffuse surface increases as the viewer approaches the source direction. A comprehensive model is developed that predicts reflectance from rough diffuse surfaces. The model accounts for complex geometric and radiometric phenomena such as masking, shadowing, and interreflections between points on the surface. Experiments have been conducted on real samples, such as, plaster, clay, sand, and cloth. All these surfaces demonstrate significant deviation from Lambertian behavior. The reflectance measurements obtained are in s...
Generalization of Lambert's Reflectance Model
 In SIGGRAPH 94
, 1994
"... Lambert's model for body reflection is widely used in computer graphics. It is used extensively by rendering techniques such as radiosity and ray tracing. For several realworld objects, however, Lambert's model can prove to be a very inaccurate approximation to the body reflectance. While ..."
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Cited by 112 (2 self)
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Lambert's model for body reflection is widely used in computer graphics. It is used extensively by rendering techniques such as radiosity and ray tracing. For several realworld objects, however, Lambert's model can prove to be a very inaccurate approximation to the body reflectance. While the brightness of a Lambertian surface is independent of viewing direction, that of a rough surface increases as the viewing direction approaches the light source direction. In this paper, a comprehensive model is developed that predicts body reflectance from rough surfaces. The surface is modeled as a collection of Lambertian facets. It is shown that such a surface is inherently nonLambertian due to the foreshortening of the surface facets. Further, the model accounts for complex geometric and radiometric phenomena such as masking, shadowing, and interreflections between facets. Several experiments have been conducted on samples of rough diffuse surfaces, such as, plaster, sand, clay, and cloth. All...
The Measurement of Highlights in Color Images
, 1988
"... In this paper, we present anapproach to colorimage understandingthat accountsforcolorvariationsdue to highlights and shading. We demonstrate that the reflected light from every point on a dielectric object. such as plastic, can be described asa linearcombination of the object color and the highligh ..."
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Cited by 111 (8 self)
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In this paper, we present anapproach to colorimage understandingthat accountsforcolorvariationsdue to highlights and shading. We demonstrate that the reflected light from every point on a dielectric object. such as plastic, can be described asa linearcombination of the object color and the highlight color. The colors of all light rays reflected from one object then form a planar cluster in the color space.The shapeof this cluster is determined by the object and highlight colors and by the object shape and illumination geometry. We present a method that exploits the difference between object color and highlight color to separate the color of every pixel into a matte component and a highlight component.This generates two intrinsic images, one showing the scene without highlights, and the other one showing only the highlights. The intrinsic images may be a useful tool for a variety of algorithms in computer vision. such as stereo vision, motion analysis, shape from shading,and shapefrom highlights. Ourmethod combines the analysis of matte and highlight reflection with a sensor model that accounts for camera limitations. This enables us to successfully run our algorithm on real images taken in a laboratory setting. We show and discuss the results.
A Model for Anisotropic Reflection
"... A reflection and refraction model for anisotropic surfaces is introduced. The anisotropy is simulated by small cylinders (added or subtracted) distributed on the anisotropic surface. Different levels of anisotropy are achieved by varying the distance between each cylinder and/or rising the cylinders ..."
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Cited by 105 (4 self)
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A reflection and refraction model for anisotropic surfaces is introduced. The anisotropy is simulated by small cylinders (added or subtracted) distributed on the anisotropic surface. Different levels of anisotropy are achieved by varying the distance between each cylinder and/or rising the cylinders more or less from the surface. Multidirectional anisotropy is modelled by orienting groups of cylinders in different direction. The intensity of the reflected light is computed by determining the visible and illuminated portion of the cylinders, taking selfblocking into account. We present two techniques to compute this in practice. In one the intensity is computed by sampling the surface of the cylinders. The other is an analytic solution. In the case of the diffuse component, the solution is exact. In the case of the specular component, an approximation is developed using a Chebyshev polynomial approximation of the specular term, and integrating the polynomial. This model can be implemented easily within most rendering system, given a suitable mechanism to define and alter surface tangents. The effectiveness of the model and the visual importance of anisotropy are illustrated with some pictures.
BOULT T.: Separation of reflection components using color and polarization
 International Journal of Computer Vision
, 1997
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Surface bidirectional reflection distribution function and the texture of bricks and tiles
, 2006
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Making Shaders More Physically Plausible
 In Fourth Eurographics Workshop on Rendering
, 1994
"... There is a need to develop shaders that not only "look good", but are more physically plausible. From physical and geometric considerations, we review the derivation of a shading equation expressing reflected radiance in terms of incident radiance and the bidirectional reflectance distribu ..."
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Cited by 73 (2 self)
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There is a need to develop shaders that not only "look good", but are more physically plausible. From physical and geometric considerations, we review the derivation of a shading equation expressing reflected radiance in terms of incident radiance and the bidirectional reflectance distribution function (BRDF). We then examine the connection between this equation and conventional shaders used in computer graphics. Imposing the additional physical constraints of energy conservation and Helmholtz reciprocity allows us to create variations of the conventional shaders that are more physically plausible. 1 Introduction Shading computation is an essential part of any rendering algorithm. Getting an exact physical model of the interaction of light with a surface is, for most surfaces occurring in the real world, a very difficult problem. Consequently, much effort has been expended on finding approximations that are both goodlooking and quickly computed. An extensive summary of these shaders ...
TemporalColor Space Analysis of Reflection
 JOURNAL OF OPTICAL SOCIETY OF AMERICA A
, 1994
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A Customizable Reflectance Model for Everyday Rendering
 In Fourth Eurographics Workshop on Rendering
, 1993
"... : This paper introduces a new reflectance model intended for realistic rendering, that includes three main features. First, it is fast and simple though it obeys to the main laws of physics (Energy conservation law, Helmholtz reciprocity rule, Microfacet theory, Fresnel equation). Second, it is defi ..."
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Cited by 60 (1 self)
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: This paper introduces a new reflectance model intended for realistic rendering, that includes three main features. First, it is fast and simple though it obeys to the main laws of physics (Energy conservation law, Helmholtz reciprocity rule, Microfacet theory, Fresnel equation). Second, it is defined by a small number of parameters which can be specified either intuitively or related to experimental measurements. Third, it is expressed by a formulation of varying complexity that can be customized according to the number of physical phenomena the user wants to include (isotropic or anisotropic reflection, homogeneous or heterogeneous materials, spectral modifications, surface selfshadowing). Keywords : Bidirectional Reflectance Distribution Function, Isotropic and Anisotropic Reflectance Model 1 Introduction Reflectance models currently used in computer graphics can be divided in two main families : either empirical models [PHON75] [BLIN77] which are computationally inexpensive bu...