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17
Interactive Rendering with Arbitrary BRDFs using Separable Approximations
 IN EUROGRAPHICS RENDERING WORKSHOP
, 1999
"... A separable decomposition of bidirectional reflectance distributions (BRDFs) is used to implement arbitrary reflectances from point sources on existing graphics hardware. Twodimensional texture mapping and compositing operations are used to reconstruct samples of the BRDF at every pixel at interact ..."
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Cited by 139 (20 self)
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A separable decomposition of bidirectional reflectance distributions (BRDFs) is used to implement arbitrary reflectances from point sources on existing graphics hardware. Twodimensional texture mapping and compositing operations are used to reconstruct samples of the BRDF at every pixel at interactive rates. A change of variables, the GramSchmidt halfangle/difference vector parameterization, improves separability. Two decomposition algorithms are also presented. The singular value decomposition (SVD) minimizes RMS error. The normalized decomposition is fast and simple, using no more space than what is required for the final representation.
Allfrequency relighting of glossy objects
 ACM TRANSACTIONS ON GRAPHICS
, 2006
"... We present a technique for interactive rendering of glossy objects in complex and dynamic lighting environments that captures interreflections and allfrequency shadows. Our system is based on precomputed radiance transfer and separable BRDF approximation. We factor glossy BRDFs using a separable de ..."
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Cited by 16 (2 self)
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We present a technique for interactive rendering of glossy objects in complex and dynamic lighting environments that captures interreflections and allfrequency shadows. Our system is based on precomputed radiance transfer and separable BRDF approximation. We factor glossy BRDFs using a separable decomposition and keep only a few loworder approximation terms, each consisting of a purely viewdependent and a purely lightdependent component. In the precomputation step, for every vertex we sample its visibility and compute a direct illumination transport vector corresponding to each BRDF term. We use modern graphics hardware to accelerate this step, and further compress the data using a nonlinear wavelet approximation. The direct illumination pass is followed by one or more interreflection passes, each of which gathers compressed transport vectors from the previous pass to produce global illumination transport vectors. To render at run time, we dynamically sample the lighting to produce a light vector, also represented in a wavelet basis. We compute the inner product of the light vector with the precomputed transport vectors, and the results are further combined with the BRDF viewdependent components to produce vertex colors. We describe acceleration of the rendering algorithm using programmable graphics hardware, and discuss the limitations and tradeoffs imposed by the hardware.
MYSZKOWSKI K.: Bidirectional texture function compression based on multilevel vector quantization
 CGF
"... The Bidirectional Texture Function (BTF) is becoming widely used for accurate representation of realworld material appearance. In this paper a novel BTF compression model is proposed. The model resamples input BTF data into a parametrization, allowing decomposition of individual view and illuminati ..."
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Cited by 15 (2 self)
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The Bidirectional Texture Function (BTF) is becoming widely used for accurate representation of realworld material appearance. In this paper a novel BTF compression model is proposed. The model resamples input BTF data into a parametrization, allowing decomposition of individual view and illumination dependent texels into a set of multidimensional conditional probability density functions. These functions are compressed in turn using a novel multilevel vector quantization algorithm. The result of this algorithm is a set of index and scale codebooks for individual dimensions. BTF reconstruction from the model is then based on fast chained indexing into the nested stored codebooks. In the proposed model, luminance and chromaticity are treated separately to achieve further compression. The proposed model achieves low distortion and compression ratios 1:233–1:2040, depending on BTF sample variability. These results compare well with several other BTF compression methods with predefined compression ratios, usually smaller than 1:200. We carried out a psychophysical experiment comparing our method with LPCA method. BTF synthesis from the model was implemented on a standard GPU, yielded interactive framerates. The proposed method allows the fast importance sampling required by eyepath tracing algorithms in image synthesis.
Hardware Rendering with Bidirectional Reflectances
, 1999
"... Contents 1 Introduction 1 2 Background 3 2.1 Reflectance Equation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.2 BRDF  Bidirectional Reflectance Distribution Function . . . . . . . . . . . . . . 4 2.3 Hardware Rendering  Prior Results . . . . . . . . . . . . . . . . . . ..."
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Cited by 9 (1 self)
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Contents 1 Introduction 1 2 Background 3 2.1 Reflectance Equation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.2 BRDF  Bidirectional Reflectance Distribution Function . . . . . . . . . . . . . . 4 2.3 Hardware Rendering  Prior Results . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.4 Goal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.5 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3 Decomposition of BRDFs 8 3.1 Singular Value Decomposition of BRDFs . . . . . . . . . . . . . . . . . . . . . . 8 3.1.1 General SVD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.1.2 SVD of a BRDF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.1.3 Drawbacks of the SVD . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 3.2 Approximate Decomposition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 3.2.1 Serial Separation of Resi
Filtered Local Shading in the Wavelet Domain
 Rendering Techniques ’97 (Proceedings of the Eighth Eurographics Workshop on Rendering
, 1997
"... : Many global illumination algorithms generate directionallyand positionallyvarying radiance data that then need to be somehow resampled and used for final shading. This operation should filter all light over the incident hemisphere through the BRDF to generate an accurate image. This can be done ..."
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Cited by 8 (3 self)
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: Many global illumination algorithms generate directionallyand positionallyvarying radiance data that then need to be somehow resampled and used for final shading. This operation should filter all light over the incident hemisphere through the BRDF to generate an accurate image. This can be done analytically for simple BRDFs, such as Lambertian or Phonglike BRDFs, but becomes more difficult in the presence of a general BRDF. This paper presents an efficient method to calculate the reflected light in a given direction, filtering over all incident light directions. The method exploits wavelet representations of incident light and of the BRDF to compute the total relfected light in a given direction. For efficiency the incident light is restricted to a Haar transformed representation, while the BRDF can be represented and compressed with any appropriate basis. The method can be used with any system that can generate projections of incident light fields onto Haar wavelet bases. 1 Intr...
Acquisition and Representation of Material Appearance for Editing and Rendering
, 2006
"... Providing computer models that accurately characterize the appearance of a wide class of materials is of great interest to both the computer graphics and computer vision communities. The last ten years has witnessed a surge in techniques for measuring the optical properties of physical materials. As ..."
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Cited by 3 (2 self)
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Providing computer models that accurately characterize the appearance of a wide class of materials is of great interest to both the computer graphics and computer vision communities. The last ten years has witnessed a surge in techniques for measuring the optical properties of physical materials. As compared to conventional techniques that rely on handtuning parametric light reflectance functions, a datadriven approach is better suited for representing complex realworld appearance. However, incorporating these representations into existing rendering algorithms and a practical production pipeline has remained an open research problem. One common approach has been to fit the parameters of an analytic reflectance function to measured appearance data. This has the benefit of providing significant compression ratios and these analytic models are already fully integrated into modern rendering algorithms. However, this approach can lead to significant approximation errors for many materials and it requires computationally expensive and numerically unstable nonlinear optimization. An alternative approach is to compress these datasets, using algorithms such as Principal Component Analysis, wavelet compression or matrix factorization. Although these techniques provide an accurate and compact representation, they do have several drawbacks. In particular,
On crossvalidation and resampling of BRDF data measurements
 In SCCG ’05: Proceedings of the 21st Spring Conference on Computer Graphics
, 2005
"... ..."
Biologically and PhysicallyBased Rendering of Natural Scenes
, 1998
"... Physicallybased rendering methods represent the core of current realistic image synthesis frameworks. These methods, through a plausible simulation of the processes of light propagation and interaction with objects, have contributed considerably to the improvement of photorealistic rendering. The s ..."
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Cited by 1 (0 self)
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Physicallybased rendering methods represent the core of current realistic image synthesis frameworks. These methods, through a plausible simulation of the processes of light propagation and interaction with objects, have contributed considerably to the improvement of photorealistic rendering. The state of art research in this area includes the simulation of natural phenomena and the incorporation of biological aspects affecting light propagation in natural environments. The search for more efficient rendering solutions is also of major interest for the rendering community. In this dissertation biologically and physicallybased models for light interaction with plant leaves are presented. Moreover, since the light that reach a plant leaf may be propagated directly from a light source or indirectly, due to multiple interactions with other objects in the environment, global illumination issues are also addressed, more specifically related to the radiosity method. This method is commonly...
Improving the reliability/cost ratio of goniophotometric measurements
 Journal of Graphics Tools
"... Abstract. Many scattering models have been presented in the graphics literature. Few of them, however, have been evaluated through comparisons with real measured data. As the demand for plausible and predictable scattering models increases, more attention is given to performing such comparisons. In ..."
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Cited by 1 (1 self)
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Abstract. Many scattering models have been presented in the graphics literature. Few of them, however, have been evaluated through comparisons with real measured data. As the demand for plausible and predictable scattering models increases, more attention is given to performing such comparisons. In this paper we examine the implementation of virtual goniphotometers used to obtain BRDF (bidirectional reflectance distribution function) and BTDF (bidirectional transmittance distribution function) records from algorithmic scattering models. These records can be compared to data from actual experiments in order to validate the models. Our discussion focuses on practical issues, namely the subdivision of the devices ’ collector sphere and the ray density required to obtain reliable BRDF and BTDF estimates. The subdivision techniques examined in this paper have been used before in publications, but the details of their computation are not readily available in the literature. Although the mathematical bound presented to determine appropriate ray densities for virtual goniphotometers is a direct generalization of a bound used for virtual spectrophotometers, it has not been published before. Our discussion of these issues is supported by practical experiments whose results are also provided in this paper. 1
Acquiring and Using Realistic Reflectance Data in Computer Graphics Images
 In Arkansas Computer Conference
, 1996
"... Analytical models of light reflection are in common use in computer graphics. However, as the sophistication of rendering methods has increased, analytical models have become less adequate for generating images. Reflectance data obtained by empirically measuring real world surfaces is needed to crea ..."
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Cited by 1 (1 self)
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Analytical models of light reflection are in common use in computer graphics. However, as the sophistication of rendering methods has increased, analytical models have become less adequate for generating images. Reflectance data obtained by empirically measuring real world surfaces is needed to create more realistic looking images. In this paper we examine several issues relevant to using measured reflectance functions in generating computer graphics images. We give an overview of the techniques involved in measuring and tabulating reflectance data. We compare and contrast measured reflectance functions with analytical illumination models, and evaluate several methods for interpolating tabulated reflectance functions. We also highlight potential areas of future research. 1 Introduction The most fundamental operation in rendering computer graphics images is the computation of how light reflects off surfaces. This computation is often performed using a local illumination model. This is ...