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Proceedings of the 17th annual conference on computer graphics and interactive techniques

作者： David Baraff Program of Computer Graphics Cornell University Ithaca NY

ISBN: (纸本)9780897913447

A formulation for the contact forces between curved surfaces in resting (non-colliding) contact is presented. In contrast to previous formulations, constraints on the allowable tangential movement between contacting surfaces are not required. Surfaces are restricted to be twice-differentiable surfaces without boundary. Only finitely many contact points between surfaces are allowed; however, the surfaces need not be convex. The formulation yields the contact forces between curved surfaces and polyhedra as well. Algorithms for performing collision detection during simulation on bodies composed of both polyhedra and strictly convex curved surfaces are also presented. The collision detection algorithms exploit the geometric coherence between successive time steps of the simulation to achieve efficient running times.

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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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Real-time robot motion planning using rasterizing computer graphics hardware 90

Real-time robot motion planning using rasterizing computer g...

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Proceedings of the 17th annual conference on computer graphics and interactive techniques

作者： Jed Lengyel Mark Reichert Bruce R. Donald Donald P. Greenberg Graduate Student Program of Computer Graphics Cornell University Ithaca N.Y. Assistant Professor and Director Computer Science Robotics Laboratory Department of Computer Science 4130 Upson HalI Cornell University Ithaca N.Y. Director Program of Computer Graphics Jacob Gould Shurman Professor of Computer Graphics Cornell University Ithaca N.Y.

ISBN: (纸本)9780897913447

We present a real-time robot motion planner that is fast and complete to a resolution. The technique is guaranteed to find a path if one exists at the resolution, and all paths returned are safe. The planner can handle any polyhedral geometry of robot and obstacles, including disjoint and highly concave unions of *** planner uses standard graphics hardware to rasterize configuration space obstacles into a series of bitmap slices, and then uses dynamic programming to create a navigation function (a discrete vector-valued function) and to calculate paths in this rasterized space. The motion paths which the planner produces are minimal with respect to an L1 (Manhattan) distance metric that includes rotation as well as *** examples are shown illustrating the competence of the planner at generating planar rotational and translational plans for complex two and three dimensional robots. Dynamic motion sequences, including complicated and non-obvious backtracking solutions, can be executed in real time.

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Improving interaction with radiosity-based lighting simulation programs 90

Improving interaction with radiosity-based lighting simulati...

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1990 Symposium on Interactive 3D graphics, I3D 1990

作者： Puech, Claude Sillion, François Vedel, Christophe Laboratoire d'Informatique Ecole Normale Supérieure 45 rue d'Ulm Paris75005 France Program of Computer Graphics Cornell University 120 Rand Hall IthacaNY14853 United States LIBNS URA 1327 CNRS France LIENS France

ISBN: (纸本)0897913515

We describe the main algorithms used in an interactive lighting simulation program based on a twopass extension of the radiosity method. The system allows interactive walk-through as other systems based on radiosity calculations. Moreover, it offers increased realism in the lighting effects by use of extended form factors which accounts for "specular reflection of diffuse light", fast production and display of progressively refined images by distribution of the calculations, good quality of the images in the early stages of the refinement by the use of "hardware light sources", "cheap" rendering of some of the specular highlights at any time by use of the built-in specular shading model, lighting modification (color, intensity of the light sources) by use of "negative light", fast simulation of mirror effects and interactive tools for controling the quality of the final image. © 1990 ACM.

关键词： Light sources

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computer graphics visualization for acoustic simulation 89

Computer graphics visualization for acoustic simulation

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16th Annual Conference on computer graphics and Interactive Techniques, SIGGRAPH 1989

作者： Stettner, Adam Greenberg, Donald P. Program of Computer Graphics Cornell University IthacaNY14853 United States

ISBN: (纸本)0897913124

computer simulations can be used to generate the spatial and temporal data describing the acoustical behavior of performance halls, but typically the analytical results are difficult to assimilate and compare. By using computer graphics to display the multi-dimensional data, substantially greater amounts of information than that conveyed by standard techniques can be communicated to the designer. This allows designs of different acoustical spaces to be tested, evaluated, and compared. An example comparing the acoustical behavior of three different concert halls demonstrates these techniques and allows for the simultaneous assimilation of much of the information necessary to evaluate the acoustical nature of a space. The use of three-dimensional images, color, animation and abstract representation allows for the comprehension of the complex results of a scientific simulation. Specifically, the simultaneous display of particular icons familiar to the discipline enabled the simultaneous presentation of up to twelve parameters. From a more general point of view, the procedures demonstrate how computer graphics can be utilized for the portrayal of multi-dimensional time dependent data. The visualization techniques are potentially useful for the display of three-dimensional vector fields in many scientific and design applications.

关键词： Data visualization

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ASSESSING THE EFFECT OF SHAPE DISTORTION IN Q9 MEMBRANE ELEMENTS

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computerS & STRUCTURES 1989年第5期33卷 1183-1190页

作者： SALMON, DC ABEL, JF Depart ment of Architecture Cornell University Ithaca NY 14853 U.S.A. School of Civil and Environmental Engineering Program of Computer Graphics Cornell University Ithaca NY 14853 U.S.A.

The Q9 membrane finite element is unable to experience arbitrary change of uniaxial curvature without the occurence of artificial membrane stains. The error which accumulates due to this inability can be significant when a large change of curvature is experienced by this element. This paper investigates the effect of element shape distortion on the accumulation of error in the Q9 membrane element, and presents two methods for evaluating shape distortion effects in problems with large changes of curvature: a series of ‘patch tests’, and single element tests.

关键词： Membranes

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A progressive refinement approach to fast radiosity image generation 88

A progressive refinement approach to fast radiosity image ge...

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15th International Conference on computer graphics and Interactive Techniques, SIGGRAPH 1988

作者： Cohen, Michael F. Chen, Shenchang Eric Wallace, John R. Greenberg, Donald P. Program of Computer Graphics Cornell University United States

ISBN: (纸本)0897912756

A reformulated radiosity algorithm is presented that produces initial images in time linear to the number of patches. The enormous memory costs of the radiosity algorithm are also eliminated by computing form-factors on-the-fly. The technique is based on the approach of rendering by progressive refinement. The algorithm provides a useful solution almost immediately which progresses gracefully and continuously to the complete radiosity solution. In this way the competing demands of realism and interactivity are accommodated. The technique brings the use of radiosity for interactive rendering within reach and has implications for the use and development of current and future graphics workstations. © 1988 ACM.

关键词： Rendering (computer graphics)

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Mixed methods for complex kinematic constraints in dynamic figure animation

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The Visual computer 1988年第6期4卷 296-305页

作者： Isaacs, Paul M. Cohen, Michael F. Program of Computer Graphics Cornell University Ithaca 14850 NY United States

Advances for achieving user control of a dynamic simulation of linked figures is presented. The formulation integrates forward and inverse kinematics specification within a mixed method of forward and inverse dynamics simulation. Kinematic specifications can be imposed through kinematic constraints embedded within the dynamics framework. Kinematic constraints may be simple (functions of one degree of freedom), or complex (functions of multiple interrelated degrees of freedom). Thus, keyframed paths, closed loops, point-to-path constraints, and collisions between links and the environment can be simulated. A simultaneous solution for unknown motion and forces of constraint is performed. A Lagrange multiplier method is outlined for incorporating these general constraints into the mathematical formulation of the equations of motion. Results from three example simulations are presented and discussed. © 1988 Springer-Verlag.

关键词： Animation Constraints Dynamics Simulation

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ON SOME RECENT EVOLUTIONS IN PERSONAL SUPERCOMPUTING AND WORKSTATION graphics

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COMMUNICATIONS IN APPLIED NUMERICAL METHODS 1988年第3期4卷 373-378页

作者： HAJJAR, JF MARTHA, LF OCONNOR, TF ABEL, JF Program of Computer Graphics Cornell University Ithaca NY 14853 U.S.A. Graduate Research Assistant Department of Structural Engineering. Graduate Student Department of Structural Engineering. Visualization Engineer/Technical Specialist. Professor of Structural Engineering.

Recent hardware advances for both enhanced computing and interactive graphics are used to improve the effectiveness of three-dimensional engineering simulations. The two examples presented, drawn from structural engin... 详细信息

关键词： computers, Personal

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The zonal method for calculating light intensities in the presence of a participating medium 87

The zonal method for calculating light intensities in the pr...

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14th Annual Conference on computer graphics and Interactive Techniques, SIGGRAPH 1987

作者： Rushmeier, Holly E. Torrance, Kenneth E. Program of Computer Graphics Rand Hall IthacaNY14853 United States Sibley School of Mechanical and Aerospace Engineering Upson Hall IthacaNY14853 United States Cornell University IthacaNY14853 United States

ISBN: (纸本)0897912276

The zonal method for calculating radiative transfer in the presence of a participating medium is applied to the generation of realistic synthetic images. The method generalizes the radiosity method and allows for emission, scattering, and absorption by a participating medium. The zonal method accounts for volume/surface interactions which have not been previously included, as well as volume/volume and surface/surface interactions. In addition, new algorithms, based on the hemi-cube formulation, are introduced for calculating the geometric factors required by the zonal method.

关键词： Light scattering

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