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147
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 79 (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...
A Microfacetbased BRDF Generator
, 2000
"... A method is presented that takes as an input a 2D microfacet orientation distribution and produces a 4D bidirectional reflectance distribution function (BRDF). This method differs from previous microfacetbased BRDF models in that it uses a simple shadowing term which allows it to handle very genera ..."
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Cited by 78 (3 self)
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A method is presented that takes as an input a 2D microfacet orientation distribution and produces a 4D bidirectional reflectance distribution function (BRDF). This method differs from previous microfacetbased BRDF models in that it uses a simple shadowing term which allows it to handle very general microfacet distributions while maintaining reciprocity and energy conservation. The generator is shown on a variety of material types.
ImageBased Reconstruction of Spatially Varying Materials
 In Proceedings of the 12th Eurographics Workshop on Rendering
, 2001
"... . The measurement of accurate material properties is an important step towards photorealistic rendering. Many realworld objects are composed of a number of materials that often show subtle changes even within a single material. Thus, for photorealistic rendering both the general surface properti ..."
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Cited by 78 (12 self)
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. The measurement of accurate material properties is an important step towards photorealistic rendering. Many realworld objects are composed of a number of materials that often show subtle changes even within a single material. Thus, for photorealistic rendering both the general surface properties as well as the spatially varying effects of the object are needed. We present an imagebased measuring method that robustly detects the different materials of real objects and fits an average bidirectional reflectance distribution function (BRDF) to each of them. In order to model the local changes as well, we project the measured data for each surface point into a basis formed by the recovered BRDFs leading to a truly spatially varying BRDF representation. A high quality model of a real object can be generated with relatively few input data. The generated model allows for rendering under arbitrary viewing and lighting conditions and realistically reproduces the appearance of the original object. 1
Cellular Texture Generation
, 1995
"... We propose an approach for modeling surface details such as scales, feathers, or thorns. These types of cellular textures require a representation with more detail than texturemapping but are inconvenient to model with handcrafted geometry. We generate ..."
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Cited by 69 (2 self)
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We propose an approach for modeling surface details such as scales, feathers, or thorns. These types of cellular textures require a representation with more detail than texturemapping but are inconvenient to model with handcrafted geometry. We generate
A New Change of Variables for Efficient BRDF Representation
 In Eurographics Workshop on Rendering
, 1998
"... We describe an idea for making decomposition of Bidirectional Reflectance Distribution Functions into basis functions more e#cient, by performing a changeofvariables transformation on the BRDFs. In particular, we propose a reparameterization of the BRDF as a function of the halfangle (i.e. the ..."
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Cited by 65 (6 self)
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We describe an idea for making decomposition of Bidirectional Reflectance Distribution Functions into basis functions more e#cient, by performing a changeofvariables transformation on the BRDFs. In particular, we propose a reparameterization of the BRDF as a function of the halfangle (i.e. the angle halfway between the directions of incidence and reflection) and a di#erence angle instead of the usual parameterization in terms of angles of incidence and reflection. Because features in common BRDFs, including specular and retroreflective peaks, are aligned with the transformed coordinate axes, the change of basis reduces storage requirements for a large class of BRDFs.
A Framework for the Analysis of Error in Global Illumination Algorithms
, 1994
"... In this paper we identify sources of error in global illumination algorithms and derive bounds for each distinct category. Errors arise from three sources: inaccuracies in the boundary data, discretization, and computation. Boundary data consist of surface geometry, reflectance functions, and emissi ..."
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Cited by 63 (3 self)
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In this paper we identify sources of error in global illumination algorithms and derive bounds for each distinct category. Errors arise from three sources: inaccuracies in the boundary data, discretization, and computation. Boundary data consist of surface geometry, reflectance functions, and emission functions, all of which may be perturbed by errors in measurement or simulation, or by simplifications made for computational efficiency. Discretization error is introduced by replacing the continuous radiative transfer equation with a finitedimensional linear system, usually by means of boundaryelements and a corresponding projection method. Finally, computational errors perturb the finitedimensional linear system through imprecise form factors, inner products, visibility, etc., as well as by halting iterative solvers after a finite number of steps. Using the error taxonomy introduced in the paper we examine existing global illumination algorithms and suggest new avenues of research. ...
Wavelength Dependent Reflectance Functions
 In Computer Graphics Proceedings, Annual Conference Series
, 1994
"... Abstract A wavelength based bidirectional reflectance function is developedfor use in realistic image synthesis. A geodesic sphere is employed to represent the BRDF, and a novel data structure is used to storethis description and to recall it for rendering purposes. A virtual goniospectrophotometer ..."
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Cited by 62 (2 self)
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Abstract A wavelength based bidirectional reflectance function is developedfor use in realistic image synthesis. A geodesic sphere is employed to represent the BRDF, and a novel data structure is used to storethis description and to recall it for rendering purposes. A virtual goniospectrophotometer is implemented by using a Monte Carloray tracer to cast rays into a surface. An optics model that incorporates phase is used in the ray tracer to simulate interference effects.An adaptive subdivision technique is applied to elaborate the data structure from rays scattered into the hemisphere above the surface.The wavelength based BRDF and virtual goniospectrophotometer are utilized to analyze and make pictures of thin films, idealizedpigmented materials, and pearlescent paints.
Monte Carlo Evaluation Of NonLinear Scattering Equations For Subsurface Reflection
"... We describe a new mathematical framework for solving a wide variety of rendering problems based on a nonlinear integral scattering equation. This framework treats the scattering functions of complex aggregate objects as firstclass rendering primitives; these scattering functions accurately account ..."
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Cited by 53 (3 self)
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We describe a new mathematical framework for solving a wide variety of rendering problems based on a nonlinear integral scattering equation. This framework treats the scattering functions of complex aggregate objects as firstclass rendering primitives; these scattering functions accurately account for all scattering events inside them. We also describe new techniques for computing scattering functions from the composition of scattering objects. We demonstrate that solution techniques based on this new approach can be more efficient than previous techniques based on radiance transport and the equation of transfer and we apply these techniques to a number of problems in rendering scattering from complex surfaces.
Illuminating Micro Geometry Based on Precomputed Visibility
, 2000
"... ing with credit is permitted. To copy otherwise, to republish, to post on servers, or to redistribute to lists, requires prior specific permission and/or a fee. Request permissions from Publications Dept, ACM Inc., fax +1 (212) 8690481, or permissions@acm.org. Illuminating Micro Geometry Based o ..."
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Cited by 44 (13 self)
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ing with credit is permitted. To copy otherwise, to republish, to post on servers, or to redistribute to lists, requires prior specific permission and/or a fee. Request permissions from Publications Dept, ACM Inc., fax +1 (212) 8690481, or permissions@acm.org. Illuminating Micro Geometry Based on Precomputed Visibility Wolfgang Heidrich # Katja Daubert Jan Kautz HansPeter Seidel MaxPlanckInstitute for Computer Science Abstract Many researchers have been arguing that geometry, bump maps, and BRDFs present a hierarchy of detail that should be exploited for efficient rendering purposes. In practice however, this is often not possible due to inconsistencies in the illumination for these different levels of detail. For example, while bump map rendering often only considers direct illumination and no shadows, geometrybased rendering and BRDFs will mostly also respect shadowing effects, and in many cases even indirect illumination caused by scattered light. In this paper, we pres...