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Reflectance and texture of realworld surfaces
 ACM TRANS. GRAPHICS
, 1999
"... In this work, we investigate the visual appearance of realworld surfaces and the dependence of appearance on scale, viewing direction and illumination direction. At ne scale, surface variations cause local intensity variation or image texture. The appearance of this texture depends on both illumina ..."
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Cited by 586 (23 self)
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In this work, we investigate the visual appearance of realworld surfaces and the dependence of appearance on scale, viewing direction and illumination direction. At ne scale, surface variations cause local intensity variation or image texture. The appearance of this texture depends on both illumination and viewing direction and can be characterized by the BTF (bidirectional texture function). At su ciently coarse scale, local image texture is not resolvable and local image intensity is uniform. The dependence of this image intensity on illumination and viewing direction is described by the BRDF (bidirectional re ectance distribution function). We simultaneously measure the BTF and BRDF of over 60 di erent rough surfaces, each observed with over 200 di erent combinations of viewing and illumination direction. The resulting BTF database is comprised of over 12,000 image textures. To enable convenient use of the BRDF measurements, we t the measurements to two recent models and obtain a BRDF parameter database. These parameters can be used directly in image analysis and synthesis of a wide variety of surfaces. The BTF, BRDF, and BRDF parameter databases have important implications for computer vision and computer graphics and and each is made publicly available.
Realistic, Hardwareaccelerated Shading and Lighting
, 1999
"... With fast 3D graphics becoming more and more available even on low end platforms, the focus in hardwareaccelerated rendering is beginning to shift towards higher quality rendering and additional functionality instead of simply higher performance implementations based on the traditional graphics pip ..."
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Cited by 53 (7 self)
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With fast 3D graphics becoming more and more available even on low end platforms, the focus in hardwareaccelerated rendering is beginning to shift towards higher quality rendering and additional functionality instead of simply higher performance implementations based on the traditional graphics pipeline. In this paper we present techniques for realistic shading and lighting using computer graphics hardware. In particular, we discuss multipass methods for high quality local illumination using physicallybased reflection models, as well as techniques for the interactive visualization of nondiffuse global illumination solutions. These results are then combined with normal mapping for increasing the visual complexity of rendered images. Although the techniques presented in this paper work at interactive frame rates on contemporary graphics hardware, we also discuss some modifications of the rendering pipeline that help to further improve both performance and quality of the proposed met...
Sudden Illumination Change Detection Using Order Consistency
 Image and Vision Computing
"... Effective change detection under dynamic illumination conditions is an active research topic. Most research has concentrated on adaptive statistical representations for the appearance of the background scene. There is limited work that develops the statistical models for background representation by ..."
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Cited by 29 (3 self)
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Effective change detection under dynamic illumination conditions is an active research topic. Most research has concentrated on adaptive statistical representations for the appearance of the background scene. There is limited work that develops the statistical models for background representation by taking into account an explicit model for the camera response function, the camera noise model, and illumination priors. Assuming a monotone but nonlinear camera response function, a Phong shading model for the surface material, and a locally constant but spatially varying illumination, we show that the sign of the difference between two pixel measurements is maintained across global illumination changes. We use this result along with a statistical model for the camera noise to develop a change detection algorithm that deals with sudden changes in illumination. The performance evaluation of the algorithm is done through simulations and on real data.
Planeparallel radiance transport for global illumination in vegetation
 In: Dorsey J , Slusallek P (eds) Rendering techniques ’97 (Proceedings of the Eighth Eurographics Rendering Workshop
, 1997
"... This document was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor the University of California nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the ..."
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Cited by 23 (5 self)
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This document was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor the University of California nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or the University of California, and shall not be used for advertising or product endorsement purposes.
Wavelet Algorithms For Illumination Computations
, 1994
"... One of the core problems of computer graphics is the computation of the equilibrium distribution of light in a scene. This distribution is given as the solution to a Fredholm integral equation of the second kind involving an integral over all surfaces in the scene. In the general case such solutions ..."
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Cited by 16 (0 self)
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One of the core problems of computer graphics is the computation of the equilibrium distribution of light in a scene. This distribution is given as the solution to a Fredholm integral equation of the second kind involving an integral over all surfaces in the scene. In the general case such solutions can only be numerically approximated, and are generally costly to compute, due to the geometric complexity of typical computer graphics scenes. For this computation both Monte Carlo and finite element techniques (or hybrid approaches) are typically used. A simplified version of the illumination problem is known as radiosity, which assumes that all surfaces are diffuse reflectors. For this case hierarchical techniques, first introduced by Hanrahan et al.[32], have recently gained prominence. The hierarchical approaches lead to an asymptotic improvement when only finite precision is required. The resulting algorithms have cost proportional to O(k² + n) versus the usual O(n²) (k is the nu...
Interactive Ray Tracing of Trimmed Bicubic Bézier Surfaces without Triangulation
 In Proceedings of WSCG
, 2005
"... By carefully exploiting the resources of today's computer hardware, interactive ray tracing recently became reality even on a single commodity PC. In most of these implementations triangles are used as the only geometric primitive. However, direct rendering of freeform surfaces would be advant ..."
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Cited by 12 (1 self)
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By carefully exploiting the resources of today's computer hardware, interactive ray tracing recently became reality even on a single commodity PC. In most of these implementations triangles are used as the only geometric primitive. However, direct rendering of freeform surfaces would be advantageous for a large number of applications, since robust tessellation of complex scenes into triangles is a very timeconsuming process. Additionally, scenes consisting of freeform surfaces require less memory and provide a much higher precision resulting in less rendering artifacts. In this paper, we present our implementation of an efficient and robust algorithm for rapidly finding intersections between rays and trimmed bicubic Bézier surfaces. Using SIMD instructions provided by many of today's CPUs, we perform the intersection test of a packet of four rays with a single Bézier surface in parallel. An optimized bounding volume hierarchy provides good initial guesses needed for fast convergence of the Newton iteration, which forms the core of our intersection algorithm. As a result, we demonstrate that it is feasible to render complex scenes of several thousand Bézier surfaces at video resolution with interactive frame rates on a single PC.
Recovery of SHGCs from a Single Intensity View
 IEEE Trans. on Pattern Analysis and Machine Intelligence
, 1996
"... Generalized Cylinders are a flexible, looselydefined class of parametric shapes capable of modeling many realworld objects. Straight Homogeneous Generalized Cylinders are an important subclass of Generalized Cylinders, whose crosssections are scaled versions of a reference curve. Although there h ..."
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Cited by 12 (1 self)
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Generalized Cylinders are a flexible, looselydefined class of parametric shapes capable of modeling many realworld objects. Straight Homogeneous Generalized Cylinders are an important subclass of Generalized Cylinders, whose crosssections are scaled versions of a reference curve. Although there has been considerable research into recovering the shape of SHGCs from their contour, this work has almost exclusively involved methods that couple contour and heuristic constraints. A rigorous approach to the problem of recovering solid parametric shape from a single intensity view should involve at least two stages: i) deriving the contour constraints, and ii) determining if additional image constraints, e.g., intensity, can be used to uniquely determine the 3D object shape. In this paper, the authors follow the approach just described. This methodology is also important for the recovery of object classes like tubes, where contour and heuristic constraints are shown to be insufficient for s...
Robust Photometric Invariant Region Detection in Multispectral Images
, 2003
"... Our aim is to detect photometric invariant regions in multispectral images robust against sensor noise. Therefore, different polar angle representations of a spectrum are examined for invariance using the dichromatic reflection model. These invariant representations take advantage of white balancing ..."
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Cited by 11 (1 self)
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Our aim is to detect photometric invariant regions in multispectral images robust against sensor noise. Therefore, different polar angle representations of a spectrum are examined for invariance using the dichromatic reflection model. These invariant representations take advantage of white balancing. Based on the camera sensitivity, a theoretical expression is obtained of the certainty associated with the polar angular representations under the influence of noise. The expression is employed by the segmentation technique to ensure robustness against sensor noise.
Volume visualizing highresolution turbulence computations
 Theor. Comput. Fluid Dyn
, 1998
"... Abstract: Using several volume visualization packages including a new package we developed called Volsh, we investigate a 25 GB dataset from a 256 3 computation of decaying quasigeostrophic turbulence. We compare surface fitting and direct volume rendering approaches, as well as a number of techniq ..."
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Cited by 8 (4 self)
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Abstract: Using several volume visualization packages including a new package we developed called Volsh, we investigate a 25 GB dataset from a 256 3 computation of decaying quasigeostrophic turbulence. We compare surface fitting and direct volume rendering approaches, as well as a number of techniques for producing featurerevealing spatial cues. We also study the pros and cons of using batch and interactive tools for visualizing the data and discuss the relative merits of using each approach. We find that each tool has its own advantages and disadvantages, and a combination of tools is most effective at exploring large fourdimensional scalar datasets. The resulting visualizations show several new phenomena in the dynamics of coherent vortices.
xcmodel: an aCADemic system
, 2000
"... xcmodel is a CAD system realized and usable in an academic environment. It integrates four packages: a 2D and a 3D modeller, an object composer and a realistic scene renderer; these subsystems can be regarded as being in constant evolution i.e. a continuous work in progress. The system summarises ou ..."
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Cited by 1 (1 self)
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xcmodel is a CAD system realized and usable in an academic environment. It integrates four packages: a 2D and a 3D modeller, an object composer and a realistic scene renderer; these subsystems can be regarded as being in constant evolution i.e. a continuous work in progress. The system summarises our knowledge and experience in geometric modelling and NURBS curves and surfaces acquired over ten years of research. xcmodel and its subsystems were designed to represent a research and teaching laboratory to experiment and learn; it is an ideal environment to develop, perfect and compare methods and algorithms in geometric modelling and graphic visualization.