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

作者： Arvo, James Torrance, Kenneth Smits, Brian Program of Computer Graphics Cornell University 580 Engineering and Theory Center Building IthacaNY14853 United States

ISBN: (纸本)0897916670

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 finite-dimensional linear system, usually by means of boundary elements and a corresponding projection method. Finally, computational errors perturb the finite-dimensional 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. © ACM 1994.

关键词： Linear systems

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ISO-contour volume rendering

ISO-contour volume rendering

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1994 Symposium on Volume Visualization, VVS 1994

作者： Arvo, James Novins, Kevin Program of Computer Graphics Cornell University 580 Engineering and Theory Center IthacaNY14853 United States IMAGIS/IMAG BP53 Grenoble Cedex 0938041 France

ISBN: (纸本)0897917413

In this paper we present a new approach to volume rendering in which curves of constant intensity in image space, or iso-contours, are computed directly for each view. The generated iso-contours can be used to drive various visualization and feature-detection algorithms. The approach imposes no restriction on the organization of the data points and can accommodate a large class of radiallysymmetric filter functions. The technique works well for both perspective and orthographic viewing projections. Each iso-contour is defined by an ordinary differential equation, which is solved numerically using a predictor-corrector method. A key element of the algorithm is the use of image intensity gradients, which we compute by means of a closed-form expression that holds at every point on the image plane. A caching algorithm is described that dramatically accelerates the gradient computations on large datasets. The algorithm is demonstrated on emission-only datasets. We conclude by describing a number of possible enhancements. © 1995 IEEE.

关键词： Volume rendering

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An exploration of three dimensional computer graphics in cockpit avionics

An exploration of three dimensional computer graphics in coc...

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Electroluminescent Materials, Devices, and Large-Screen Displays 1993

作者： Pruyn, Peter W. Greenberg, Donald P. Program of Computer Graphics Cornell University IthacaNY14853 United States

There has been a trend during the 1980s in commercial airliner cockpits of replacing many of the round-faced, analog instruments with CRT displays. However, the computer graphics technology that is utilized in these CRT displays is more than ten years old and frequently simply mimics the appearance of the older, analog displays. We will explore some of the possible uses of state of the art, three dimensional computer graphics as an integrator and as a visualizer of flight information. Using computer models of primary navigational features and the ray-Tracing rendering technique, three-dimensional, symbolic representations of flight information are explored. Right tasks investigated include enroute navigation, collision avoidance, weather, and the instrument approach. © 1993 SPIE. All rights reserved.

关键词： Three dimensional computer graphics

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Painting with light 93

Painting with light

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20th International Conference on computer graphics and Interactive Techniques, SIGGRAPH 1993

作者： Schoeneman, Chris Dorsey, Julie Smits, Brian Arvo, James Greenberg, Donald Program of Computer Graphics Cornell University IthacaNY14853 United States

ISBN: (纸本)0897916018

We present a new approach to lighting design for image synthesis. It is based on the inverse problem of determining light settings for an environment from a description of the desired solution. The method is useful for determining light intensities to achieve a desired effect in a computer simulation and can be used in conjunction with any rendering algorithm. Given a set of lights with fixed positions, we determine the light intensities and colors that most closely match the target image painted by the designer using a constrained least squares approach. We describe an interactive system that allows flexible input and display of the solution. © 1993 ACM.

关键词： Ray tracing

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Combining hierarchical radiosity and discontinuity meshing 93

Combining hierarchical radiosity and discontinuity meshing

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20th International Conference on computer graphics and Interactive Techniques, SIGGRAPH 1993

作者： Lischinski, Dani Tampieri, Filippo Greenberg, Donald P. Program of Computer Graphics Cornell University IthacaNY14853 United States

ISBN: (纸本)0897916018

We introduce a new approach for the computation of view-independent solutions to the diffuse global illumination problem in polyhedral environments. The approach combines ideas from hierarchical radiosity and discontinuity meshing to yield solutions that are accurate both numerically and visually. First, we describe a modified hierarchical radiosity algorithm that uses a discontinuity-driven subdivision strategy to achieve better numerical accuracy and faster convergence. Second, we present a new algorithm based on discontinuity meshing that uses the hierarchical solution to reconstruct an object-space approximation to the radiance function that is visually accurate. Our results show significant improvements over both hierarchical radiosity and discontinuity meshing algorithms. © 1993 ACM.

关键词： Approximation algorithms

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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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Galerkin radiosity: A higher order solution method for global illumination 93

Galerkin radiosity: A higher order solution method for globa...

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20th International Conference on computer graphics and Interactive Techniques, SIGGRAPH 1993

作者： Zatz, Harold R. Cornell Program of Computer Graphics United States Rhythm and Hues Studios Inc. 910 North Sycamore Ave. HollywoodCA90038 United States

ISBN: (纸本)0897916018

This paper presents an alternative radiosity formulation using piecewise smooth radiance functions that incorporates curved surfaces directly. Using the Galerkin integral equation technique as a mathematical foundation, surface radiance functions are approximated by polynomials. This model eliminates the need for a posteriori rendering interpolation, and allows the direct use of non-planar parametric surfaces. Convergence problems due to singularities in the radiosity kernel are analyzed and rectified, and sources of approximation error are examined. The incorporation of a shadow masking technique vastly reduces the need for meshing and associated storage space-accurate radiosity calculations can often be made with no meshing. The technique is demonstrated on traditional radiosity scenes, as well as environments with untessellated curved surfaces. © 1993 ACM.

关键词： Galerkin methods

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Controlled precision volume integration

Controlled precision volume integration

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Proceedings of the 1992 Workshop on Volume Visualization

作者： Novins, Kevin Arvo, James Program of Computer Graphics Cornell University Ithaca 14853 NY United States

ISBN: (纸本)0897915275

Traditional methods for evaluating the low-Albedo volume rendering integral do not include bounds on the magnitude of approximation error. In this paper, we examine three techniques for solving this integral with error bounds: Trapezoid rule, Simpson's rule, and a power series method. In each case, the expression for the error bound provides a mechanism for computing the integral to any specified precision. The formulations presented are appropriate for polynomial reconstruction from point samples;however, the approach is considerably mom general. The three techniques we present differ in relative efficiency for computing results to a given precision. The trapezoid rule and Simpson's rule are most efficient for low-to medium-precision solutions. The power series method converges rapidly to a machine precision solution, providing both an efficient means for high-Accuracy volume rendering, and a reference standard by which other approximations may be measured. ©1992 ACM.

关键词： Numerical quadrature Scientific visualization Volume rendering

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Comparison of Mixed-Mode Stress-Intensity Factors Obtained Through Displacement Correlation, J-Integral Formulation, and Modified Crack-Closure Integral 22

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22nd National Symposium on Fracture Mechanics, NSFM 1990

作者： Bittencourt, Tulio N. Barry, Ahmabou Ingraffea, Anthony R. Department of Structural Engineering School of Civil and Environmental Engineering Program of Computer Graphics Fracture Group Cornell University IthacaNY14850 United States

ISBN: (纸本)9780803114401

This paper presents a comparison among stress-intensity factors for mixed-mode two-dimensional problems obtained through three different approaches: displacement correlation, J-integral, and modified crack-closure integral. All mentioned procedures involve only one analysis step and are incorporated in the post-processor page of a finite element computer code for fracture mechanics analysis (FRANC). Results are presented for a closed-form solution problem under mixed-mode conditions. The accuracy of these described methods then is discussed and analyzed in the framework of the their numerical results. The influence of the differences among the three methods on the predicted crack trajectory of general problems is also discussed. © 1992 by ASTM International.

关键词： Stress intensity factors

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Predicting reflectance functions from complex surfaces 92

Predicting reflectance functions from complex surfaces

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Proceedings of the 19th annual conference on computer graphics and interactive techniques

作者： Stephen H. Westin James R. Arvo Kenneth E. Torrance Program of Computer Graphics Cornell University IthacaNewYork

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