A new general reflectance model for computer graphics is presented. The model is based on physical optics and describes specular, directional diffuse, and uniform diffuse reflection by a surface. The reflected light pattern depends on wavelength, incidence angle, two surface roughness parameters. and surface refractive index. The formulation is self consistent in terms of polarization, surface roughness,

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...

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 non-Lambertian 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...

: Lambert's model for diffuse reflection is extensively used in computational vision. For several real-world 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. Experiments have been conducted on real samples, such as, plaster, clay, and sand. The reflectance measurements obtained are in strong agreement with the reflectance predicted by the proposed model. 1 Introduction A surface that obeys Lambert's Law appears equally bright from all viewing directions [ Lambert-1760 ] . This model for diffuse reflection was advanced by Lambert over 200 years ago and remains one of the most widely used models in machine vision. It is used explicitly by shape recovery techniques s...

The light reflected from a surface depends on the scene geometry, the incident illumination and the surface material. One of the properties of the material is its albedo r(l) and its variation with respect to wavelength. The albedo of a surface is purely a physical property. Our perception of albedo is commonly referred to as colour. This paper presents a novel methodology for extracting the albedo of the various materials in the scene independent of incident light and scene geometry. A scene is captured under different narrow-band colour filters and the spectral derivatives of the scene are computed. The resulting spectral derivatives form a spectral gradient at each pixel. This spectral gradient is a normalized albedo descriptor which is invariant to scene geometry and incident illumination for diffuse surfaces.