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Now showing 1 - 7 of 7
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    Image-Based BRDF Measurement Including Human Skin
    (The Eurographics Association, 1999) Marschner, Stephen R.; Westin, Stephen H.; Lafortune, Eric P. F.; Torrance, Kenneth E.; Greenberg, Donald P.; Dani Lischinski and Greg Ward Larson
    We present a new image-based process for measuring the bidirectional reflectance of homogeneous surfaces rapidly, completely, and accurately. For simple sample shapes (spheres and cylinders) the method requires only a digital camera and a stable light source. Adding a 3D scanner allows a wide class of curved near-convex objects to be measured. With measurements for a variety of materials from paints to human skin, we demonstrate the new method s ability to achieve high resolution and accuracy over a large domain of illumination and reflection directions. We verify our measurements by tests of internal consistency and by comparison against measurements made using a gonioreflectometer.
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    Local Illumination Environments for Direct Lighting Acceleration
    (The Eurographics Association, 2002) Fernandez, Sebastian; Bala, Kavita; Greenberg, Donald P.; P. Debevec and S. Gibson
    Computing high-quality direct illumination in scenes with many lights is an open area of research. This paper presents a world-space caching mechanism called local illumination environments that enables interactive direct illumination in complex scenes on a cluster of off-the-shelf PCs. A local illumination environment (LIE) caches geometric and radiometric information related to direct illumination. A LIE is associated with every octree cell constructed over the scene. Each LIE stores a set of visible lights, with associated occluders (if they exist). LIEs are effective at accelerating direct illumination because they both eliminate shadow rays for fully visible and fully occluded regions of the scene, and decrease the cost of shadow rays in other regions. Shadow ray computation for the partially occluded regions is accelerated using the cached potential occluders. One important implication of storing occluders is that rendering is accelerated while producing accurate hard and soft shadows. This paper also describes a simple perceptual metric based on Weber s law that further improves the effectiveness of LIEs in the fully visible and partially occluded regions. LIE construction is view-driven, continuously refined, and asynchronous with the shading process. In complex scenes of hundreds of thousands of polygons with up to a hundred lights, the LIEs improve rendering performance by 10x to 30x over a traditional ray tracer.
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    A Testbed for Architectural Modeling
    (Eurographics Association, 1991) Hall, Roy; Bussan, Mimi; Georgiades, Priamos; Greenberg, Donald P.
    This paper describes the philosophy and implementation of a modeling system that is easy to use yet addresses some of the difficulties of design. It does this by supporting concurrent schematic and geometric representations, alternative solution schemes, ambiguous and incomplete specification, and multiple levels of detail through a wide range of scale. The system treats an object as a hierarchical record of design decisions and treats geometry as an artifact of traversing a decision tree. For displaying geometry, the system incorporates fast rendering techniques for interactive use and global illumination algorithms for design evaluation and final presentation. The system is intended to serve as an extensible testbed for long-term research in modeling and design. Vigorous use by students in the Department of Architecture at Cornell is the vehicle for system evaluation and redirection of research goals.
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    Using Perceptual Texture Masking for Efficient Image Synthesis
    (Blackwell Publishers, Inc and the Eurographics Association, 2002) Walter, Bruce; Pattanaik, Sumanta N.; Greenberg, Donald P.
    Texture mapping has become indispensable in image synthesis as an inexpensive source of rich visual detail. Less obvious, but just as useful, is its ability to mask image errors due to inaccuracies in geometry or lighting. This ability can be used to substantially accelerate rendering by eliminating computations when the resulting errors will be perceptually insignificant.Our new method precomputes the masking ability of textures using aspects of the JPEG image compression standard. This extra information is stored as threshold elevation factors in the texture's mip-map and interpolated at image generation time as part of the normal texture lookup process. Any algorithm which uses error tolerances or visibility thresholds can then take advantage of texture masking. Applications to adaptive shadow testing, irradiance caching, and path tracing are demonstrated.Unlike prior methods, our approach does not require that initial images be computed before masking can be exploited and incurs only negligible runtime computational overhead. Thus, it is much easier to integrate with existing rendering systems for both static and dynamic scenes and yields computational savings even when only small amounts of texture masking are present.Categories and Subject Descriptors (according to ACM CCS): I.3.7 [Computer Graphics]: Color, shading, shadowing, and texture
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    A Testbed for Image Synthesis
    (Eurographics Association, 1991) Trumbore, Ben; Lytle, Wayne; Greenberg, Donald P.
    Image Synthesis research combines new ideas with existing techniques. A collection of software modules that provide such techniques is extremely useful for simplifying the development process. We describe the design and implementation of a new Testbed for Image Synthesis that provides such support. This Testbed differs from previous Testbeds in both its goals and its design decisions. The Testbed design addresses the problems of high model complexity, complicated global illumination algorithms and coarse grain parallel processing environments. The implementation is modular, portable and extensible. It allows for statistical comparison of algorithms and measurement of incremental image improvements, as well as quantitative comparison of Testbed images and light reflectance measured from physical models. The Testbed is designed to interface with any available modeling system. This compatibility was achieved through careful design of the data format that represents environments. The software modules of the Testbed are organized in a hierarchical fashion, simplifying application programming.
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    Disruptive Technologies in Computer Graphics: Past, Present, and Future
    (The Eurographics Association, 1999) Greenberg, Donald P.; Dani Lischinski and Greg Ward Larson
    The history and famous landmarks of computer graphics hardware are well known. Starting with Ivan Sutherland s Sketchpad system in the early 1960 s, the first generation of computer graphics hardware consisted of calligraphic (vector) displays capable of drawing complex three-dimensional wireframe models at interactive rates. In the early 1970 s expensive color frame buffers with the capability for displaying static color images were introduced. Although more and more intelligence was added to these frame buffers, Jim Clark s geometry engine and the first graphics workstations were not introduced until the 1980 s. During the 1970 s, only the very costly and specialized hardware used for military and aerospace simulations was capable of real-time surface color display.
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    Enhancing and Optimizing the Render Cache
    (The Eurographics Association, 2002) Walter, Bruce; Drettakis, George; Greenberg, Donald P.; P. Debevec and S. Gibson
    Interactive rendering often requires the use of simplified shading algorithms with reduced illumination fidelity. Higher quality rendering algorithms are usually too slow for interactive use. The render cache is a technique to bridge this performance gap and allow ray-based renderers to be used in interactive contexts by providing automatic sample interpolation, frame-to-frame sample reuse, and prioritized sampling. In this paper we present several extensions to the original render cache including predictive sampling, reorganized computation for better memory coherence, an additional interpolation filter to handle sparser data, and SIMD acceleration. These optimizations allow the render cache to scale to larger resolutions, reduce its visual artifacts, and provide better handling of low sample rates. We also provide a downloadable binary to allow researchers to evaluate and use the render cache.