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18th Annual Conference on computer graphics and Interactive Techniques, SIGGRAPH 1991

作者： Kirk, David Arvo, James California Institute of Technology Computer Graphics 350-74 PasadenaCA91125 United States Program of Computer Graphics Cornell University IthacaNY14853 United States

ISBN: (纸本)0897914368

We examine a class of adaptive sampling techniques employed in image synthesis and show that those commonly used for efficient anti-aliasing are statistically biased. This bias is dependent upon the image function being sampled as well as the strategy for determining the number of samples to use. It is most prominent in areas of high contrast and is attributable to early stages of sampling systematically favoring one extreme or the other. If the expected outcome of the entire adaptive sampling algorithm is considered, we find that the bias of the early decisions is stiO present in the final estimator. We propose an alternative strategy for performing adaptive sampling that is unbiased but potentially more costly. We conclude that it may not always be practical to mitigate this source of bias, but as a source of error it should be considered when high accuracy and image fidelity are a central concern. © 1991 ACM.

关键词： Anti-aliasing

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The back-buffer algorithm: An extension of the radiosity method to dynamic environments

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The Visual computer 1986年第5期2卷 298-306页

作者： Baum, Daniel R. Wallace, John R. Cohen, Michael F. Greenberg, Donald P. Cornell University Program of Computer Graphics Cornell University Ithaca 14853 NY 120 Rand Hall United States

An efficient algorithm is introduced for the production of realistic image sequences of dynamic environments. The practicality of the radiosity method, which computes the interreflection of light within complex diffuse environments independent of viewpoint, is extended to dynamic environments where the paths of moving objects have been predefined. The algorithm takes advantage of the object coherence between static portions of an environment. A preprocessing stage executes once for a given image sequence and precalculates constant geometrical relationships in the environment. When the environment geometry changes, an update stage determines the global illumination using information provided by the preprocessor and the current positions of all moving objects. Test environments show speedups of at least twenty-five times over previous radiosity methods. © 1986 Springer-Verlag.

关键词： computer animation Light reflectance models Radiosity

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Direct illumination with lazy visibility evaluation 99

Direct illumination with lazy visibility evaluation

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26th Annual Conference on computer graphics and Interactive Techniques, SIGGRAPH 1999

作者： Hart, David Dutré, Philip Greenberg, Donald P. Program of Computer Graphics Cornell University 580 Rhodes Hall IthacaNY14850 United States

ISBN: (纸本)0201485605

In this paper we present a technique for computing the direct lighting in a three-dimensional scene containing area light sources. Our method correctly handles partial visibility between luminaires and receivers, and is able to efficiently generate accurate soft shadows in scenes modeled with general bidirectional reflectance distribution functions. In most current algorithms, the form factor between a light source and receiver is computed using a stochastic ray casting approach which evaluates partial visibility. Such an approach often leads to noisy artifacts or aliasing problems. Generating significantly more rays is often the only solution to improving image quality. Our approach first stores visibility information in the image plane, using lazy evaluation of the visibility function. In a second phase, illumination values for each pixel are generated, using analytic or stochastic integration. Soft shadows and other shading effects are generated with high accuracy in less time than with existing shading algorithms. Coherence in specific blocker light source relationships across the image plane is exploited to amortize the cost of analytic form factor calculations. By storing information in the image plane, our method is currently designed for generating a single image, and is thus view-dependent. Copyright ACM 1999.

关键词： Distribution functions

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A perceptually based physical error metric for realistic image synthesis 99

A perceptually based physical error metric for realistic ima...

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26th Annual Conference on computer graphics and Interactive Techniques, SIGGRAPH 1999

作者： Ramasubramanian, Mahesh Pattanaik, Sumanta N. Greenberg, Donald P. Program of Computer Graphics Cornell University 580 Rhodes Hall IthacaNY14853 United States

ISBN: (纸本)0201485605

We introduce a new concept for accelerating realistic image synthesis algorithms. At the core of this procedure is a novel physical error metric that correctly predicts the perceptual threshold for detecting artifacts in scene features. Built into this metric is a computational model of the human visual system's loss of sensitivity at high background illumination levels, high spatial frequencies, and high contrast levels (visual masking). An important feature of our model is that it handles the luminance-dependent processing and spatially dependent processing independently. This allows us to precompute the expensive spatially-dependent component, making our model extremely efficient. We illustrate the utility of our procedure with global illumination algorithms used for realistic image synthesis. The expense of global illumination computations is many orders of magnitude higher than the expense of direct illumination computations and can greatly benefit by applying our perceptually based technique. Results show our method preserves visual quality while achieving significant computational gains in areas of images with high frequency texture patterns, geometric details, and lighting variations. Copyright ACM 1999.

关键词： Errors

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A multiscale model of adaptation and spatial vision for realistic image display 98

A multiscale model of adaptation and spatial vision for real...

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25th Annual Conference on computer graphics and Interactive Techniques, SIGGRAPH 1998

作者： Pattanaik, Sumanta N. Ferwerda, James A. Fairchild, Mark D. Greenberg, Donald P. Program of Computer Graphics Cornell University 580 Rhodes Hall Ithaca NY 14853 United States

ISBN: (纸本)0897919998

In this paper we develop a computational model of adaptation and spatial vision for realistic tone reproduction. The model is based on a multiscale representation of pattern, luminance, and color processing in the human visual system. We incorporate the model into a tone reproduction operator that maps the vast ranges of radiances found in real and synthetic scenes into the small fixed ranges available on conventional display devices such as CRT's and printers. The model allows the operator to address the two major problems in realistic tone reproduction: wide absolute range and high dynamic range scenes can be displayed;and the displayed images match our perceptions of the scenes at both threshold and suprathresh-old levels to the degree possible given a particular display device. Although in this paper we apply our visual model to the tone reproduction problem, the model is general and can be usefully applied to image quality metrics, image compression methods, and perceptually-based image synthesis algorithms.

关键词： Display devices

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A clustering algorithm for radiosity in complex environments 94

A clustering algorithm for radiosity in complex environments

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21st Annual Conference on computer graphics and Interactive Techniques, SIGGRAPH 1994

作者： Smits, Brian Arvo, James Greenberg, Donald Program of Computer Graphics Cornell University 580 ETC Building IthacaNY14853 United States

ISBN: (纸本)0897916670

We present an approach for accelerating hierarchical radiosity by clustering objects. Previous approaches constructed effective hierarchies by subdividing surfaces, but could not exploit a hierarchical grouping on existing surfaces. This limitation resulted in an excessive number of initial links in complex environments. Initial linking is potentially the most expensive portion of hierarchical radiosity algorithms, and constrains the complexity of the environments that can be simulated. The clustering algorithm presented here operates by estimating energy transfers between collections of objects while maintaining reliable error bounds on each transfer. Two methods of bounding the transfers are employed with different tradeoffs between accuracy and time. In contrast with the O(s2) time and space complexity of the initial linking in previous hierarchical radiosity algorithms, the new methods have complexities of O(slogs) and O(s) for both time and space. Using these methods we have obtained speedups of two orders of magnitude for environments of moderate complexity while maintaining comparable accuracy. © ACM 1994.

关键词： Clustering algorithms

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Interactive global illumination in dynamic scenes 02

Interactive global illumination in dynamic scenes

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ACM Transactions on graphics;Proceedings of ACM SIGGRAPH 2002

作者： Tole, Parag Pellacini, Fabio Walter, Bruce Greenberg, Donald P. Program of Computer Graphics Cornell University 580 Rhodes Hall Ithaca NY 14853 United States

ISBN: (纸本)9781581135213

In this paper, we present a system for interactive computation of global illumination in dynamic scenes. Our system uses a novel scheme for caching the results of a high quality pixel-based renderer such as a bidirectional path tracer. The Shading Cache is an object-space hierarchical subdivision mesh with lazily computed shading values at its vertices. A high frame rate display is generated from the Shading Cache using hardware-based interpolation and texture mapping. An image space sampling scheme refines the Shading Cache in regions that have the most interpolation error or those that are most likely to be affected by object or camera motion. Our system handles dynamic scenes and moving light sources efficiently, providing useful feedback within a few seconds and high quality images within a few tens of seconds, without the need for any pre-computation. Our approach allows us to significantly outperform other interactive systems based on caching ray-tracing samples, especially in dynamic scenes. Based on our results, we believe that the Shading Cache will be an invaluable tool in lighting design and modelling while rendering.

关键词： Three dimensional computer graphics

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Microfacet Models for Refraction through Rough Surfaces

Microfacet Models for Refraction through Rough Surfaces

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18th Eurographics Symposium on Rendering Techniques, EGSR 2007

作者： Walter, Bruce Marschner, Stephen R. Li, Hongsong Torrance, Kenneth E. Program of Computer Graphics Cornell University United States Beijing Institute of Technology China

ISBN: (纸本)9783905673524

Microfacet models have proven very successful for modeling light reflection from rough surfaces. In this paper we review microfacet theory and demonstrate how it can be extended to simulate transmission through rough surfaces such as etched glass. We compare the resulting transmission model to measured data from several real surfaces and discuss appropriate choices for the microfacet distribution and shadowing-masking functions. Since rendering transmission through media requires tracking light that crosses at least two interfaces, good importance sampling is a practical necessity. Therefore, we also describe efficient schemes for sampling the microfacet models and the corresponding probability density functions. © The Eurographics Association 2007.

关键词： Light reflection

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Fast, minimum storage ray/triangle intersection 05

Fast, minimum storage ray/triangle intersection

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ACM SIGGRAPH 2005 International Conference on computer graphics and Interactive Techniques, SIGGRAPH 2005

作者： Möller, Tomas Trumbore, Ben Prosolvia Claxus AB Chalmers University of Technology Sweden Program of Computer Graphics Cornell University United States

ISBN: (纸本)9781450378338

We present a clean algorithm for determining whether a ray intersects a triangle. The algorithm translates the origin of the ray and then changes the base of that vector which yields a vector (t u v)T, where t is the distance to the plane in which the triangle lies and (u, v) represents the coordinates inside the triangle. One advantage of this method is that the plane equation need not be computed on the fly nor be stored, which can amount to significant memory savings for triangle meshes. As we found our method to be comparable in speed to previous methods, we believe it is the fastest ray/triangle intersection routine for triangles which do not have precomputed plane equations.

关键词： Ray tracing

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Use of networked workstations for parallel nonlinear structural dynamic simulations of rotating bladed-disk assemblies

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Computing Systems in Engineering 1993年第4-6期4卷 521-530页

作者： Hsien, Shang-Hsien Abel, J.F. School of Civil and Environmental Engineering Program of Computer Graphics Cornell University Ithaca NY 14853-3501 Hollister Hall United States

The principal objective of this research is to investigate, develop and demonstrate coarse-grained, parallel-processing strategies for nonlinear dynamic simulations of rotating bladed-disk assemblies. The parallel-processing strategies addressed include numerical algorithms for parallel nonlinear solutions and techniques to effect load balancing among processors. The parallel environment employed is a distributed-memory, coarse-grained one consisting of networked workstations. A parallel explicit time integration method has been implemented for transient nonlinear solutions of rotating bladed-disk assemblies. Automatic domain partitioning techniques have been investigated for load balancing among processors. Advanced computing environments, data structures and interactive computer graphics all contribute to an integrated parallel finite element analysis system to facilitate more efficient and powerful dynamic simulations. © 1994.

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