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23rd Annual Conference (EUROgraphics 2002)

作者： Walter, Bruce Pattanaik, Sumanta N. Greenberg, Donald P. Program of Computer Graphics 580 Rhodes Hall Cornell University Ithaca NY 14853 United States University of Central Florida SEECS Department of Computer Science Orlando FL 32816-2362 United States

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.

关键词： Image compression

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Visual equivalence: An object-based approach to image quality

Visual equivalence: An object-based approach to image qualit...

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16th Color Imaging Conference: Color Science and Engineering Systems, Technologies, and Applications

作者： Ferwerda, James A. Ramanarayanan, Ganesh Walter, Bruce Bala, Kavita Munsell Color Science Laboratory Center for Imaging Science Rochester Institute of Technology Rochester NY United States Department of Computer Science Cornell University Ithaca NY United States Program of Computer Graphics Cornell University Ithaca NY United States

ISBN: (纸本)9780892082810

In this paper we introduce a new approach to characterizing image quality: visual equivalence, Images are visually equivalent if they convey the same information about object appearance even if they are visibly different. In a series of psychophysical experiments we explore how object geometry, material, and illumination interact to produce images that are visually equivalent, and we identify how two kinds of transformations on illumination fields (blurring and warping) influence observers' judgments of equivalence. We use the results of the experiments to derive metrics that can serve as visual equivalence predictors (VEPs) and we generalize these metrics so they can be applied to novel objects and scenes. Finally we validate the predictors in a confirmatory study, and show that they reliably predict observer's judgments of equivalence. Visual equivalence is a significant new approach to measuring image quality that goes beyond existing visible difference metrics by leveraging the fact that some kinds of image differences do not matter to human observers. By taking advantage of higher order aspects of visual object coding, visual equivalence metrics should enable the development of powerful new classes of image capture, compression, rendering, and display algorithms.

关键词： Image quality

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computer Simulation of Foliage Shading in Building Energy Loads 79

Computer Simulation of Foliage Shading in Building Energy Lo...

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Design Automation Conference

作者： M. Schiler D.P. Greenberg Program of computer Graphics Cornell University Ithaca NY USA

The calculation of building thermal loads using the computer has been an accepted practice for several years. A substantial amount of research and theoretical investigation has been expended in attempts to accurately quantify a building's thermal behavior. A number of existing simulation packages acceptably model this behavior.1,2,3,4,5,6The advantages of simulation are obvious, not only for the predictive information with respect to operating costs or fuel consumption, but as a potential aid for preliminary design. The influence and tradeoffs of a large number of design variables such as siting, orientation, window area, thermal resistivity, surface/volume ratios, and cost can all be examined at an early stage in the design process.

关键词： computer simulation computer graphics Information analysis Computational modeling Packaging Costs Analytical models Tree graphs Thermal loading Predictive models

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An interactive graphics environment for architectural energy simulation 82

An interactive graphics environment for architectural energy...

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Proceedings of the 9th annual conference on computer graphics and interactive techniques

作者： Jon H. Pittman Donald P. Greenberg Program of Computer Graphics Cornell University Ithaca New York

ISBN: (纸本)9780897910767

An interactive computer graphics system has been developed for the architecture profession which provides a “design environment” for the evaluation of building energy consumption. The system includes an integrated set of graphic input tools which generate the geometric and attribute data necessary for the determination of thermal load in buildings. In addition, a comprehensive set of graphical output routines has been created to allow the designer to visually interpret the results of alternative design strategies.

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Path specification and path coherence 82

Path specification and path coherence

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Proceedings of the 9th annual conference on computer graphics and interactive techniques

作者： Kim L. Shelley Donald P. Greenberg Program of Computer Graphics Cornell University Ithaca New York

ISBN: (纸本)9780897910767

This paper presents an interactive method for specifying a path in space and time through a three-dimensional environment. A sequence is generated by showing the series of views along the path. The sequence is previewed on a vector scope, and after it is interactively refined, each frame is rendered on a raster device. The path is represented by a B-spline to provide smooth, continuous motion. The timing along the path is also defined by a B-spline so that changes in velocity are smooth. The use of “path coherence” is introduced. The utilization of the available data from the a priori temporal and spatial path definition holds great promise for frame to frame coherence. The path coherence can be used to reduce the number of polygons which need to be considered in a viewed environment. This reduction makes the previewing of complex environments appear less cluttered. Furthermore, the computational expense of the culling and sorting operations in the visible line/surface determination is reduced. One sample usage of this is a tree-structured partitioned environment where the priority ordering of the environment must be changed only when the path crosses a partition boundary.

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VR - A reality check?

VR - A reality check?

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IEEE Virtual Reality 2005

作者： Smith, Randall C. Sandin, Dan Fisher, Brian D. Westin, Stephen H. General Motors R and D Electronic Visualization Lab. U. Illinois Chicago School of Interactive Arts and Technology Simon Fraser University Program of Computer Graphics Cornell University

Within the large spectrum of possible VR application areas, automotive applications were among the first to appear, and are among the most demanding. Technology has not been sufficiently sophisticated for many tasks. The troubling thought is that we are happy to push the technology envelope, but don't really know how useful this technology is, or can be. Could I do my job even if I had a real-time, ortho-stereoscopic, head-tracked, multi-viewer, wide-field-of-view, high-dynamic-range display with eye-limiting acuity?

关键词： Virtual reality

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A fast and accurate light reflection model 92

A fast and accurate light reflection model

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

作者： Xiao D. He Patrick O. Heynen Richard L. Phillips Kenneth E. Torrance David H. Salesin Donald P. Greenberg Program of Computer Graphics Cornell University Ithaca New York Program of Computer Graphics Cornell University Ithaca New York Los Alamos National Laboratory Los Alamos New Mexico

No abstract available.

ISBN: (纸本)9780897914796

No abstract available.

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A NUMERICAL PROCEDURE FOR SIMULATION OF HYDRAULICALLY-DRIVEN FRACTURE PROPAGATION IN POROELASTIC MEDIA

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INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS 1990年第1期14卷 27-+页

作者： BOONE, TJ INGRAFFEA, AR Program of Computer Graphics and School of Civil and Environmental Engineering Cornell University Ithaca NY 14853-3501 U.S.A.

A procedure for numerical approximation to two-dimensional, hydraulically-driven fracture propagation in a poroelastic material is described. The method uses a partitioned solution procedurè to solve a finite element approximation to problems described by the theory of poroelasticity, in conjunction with a finite difference approximation for modelling fluid flow along the fracture. An equilibrium fracture model based on a generalized, Dugdale–Barenblatt concept is used to determine the fracture dimensions. An important feature is that the fracture length is a natural product of the solution algorithm. Two example problems verify the accuracy of the numerical procedure and a third example illustrates a fully-coupled simulation of fracture propagation. Photographs taken from a high-performance engineering workstation provide insight into the nature of the coupling among the physical phenomena.

关键词： Porous Materials

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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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Transparency for computer synthesized images 79

Transparency for computer synthesized images

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6th Annual Conference on computer graphics and Interactive Techniques, SIGGRAPH 1979

作者： Kay, Douglas Scott Greenberg, Donald Program of Computer Graphics Cornell University United States Sundance Productions Inc. Acme Cartoon Co. Inc. 7141 Envoy Ct. DallasTX75247 United States

ISBN: (纸本)0897910044

Simple transparency algorithms which assume a linear transparency over an entire surface are the type most often employed to produce computer synthesized images of transparent objects with curved surfaces. Although most of the images created with these algorithms do give the impression of transparency, they usually do not look realistic. One of the most serious problems is that the intensity of the light that is transmitted through the objects is generally not proportional to the amount of material through which it must pass. Another problem is that the image seen behind the objects is not distorted as would naturally occur when the light is refracted as it passes through a material of different density. Use of a non-linear transparency algorithm can provide a great improvement in the realism of an image at a small additional cost. Making the transparency proportional to the normal to the surface causes it to decrease towards the edges of the surface where the path of the light through the object is longer. The exact simulation of refraction, however, requires that each sight ray be individually traced from the observer, through the picture plane and through each transparent object until an opaque surface is intersected. Since the direction of the ray would change as each material of differing optical density was entered, the hidden surface calculations required would be very time consuming. However, if a few assumptions are made about the geometry of each object and about the conditions under which they are viewed, a much simplier algorithm can be used to approximate the refractive effect. This method proceeds in a back to front order, mapping the current background image onto the next surface, until all surfaces have been considered. © 1979 ACM.

关键词： Transparency

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