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Using Perceptual Texture Masking for Efficient Image Synthesis

computer graphics Forum 2003年第3期21卷

作者： Bruce Walter Sumanta N. Pattanaik Donald P. Greenberg Cornell University † Program of Computer Graphics 580 Rhodes Hall Cornell University Ithaca NY 14853 USA † University of Central Florida SEECS Department of Computer Science Room 250 Orlando FL 32816-2362 USA University of Central Florida

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

关键词： Visual Perception Perceptual Rendering Texture Mapping JPEG

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Efficient bounded adaptive tessellation of displacement maps

Efficient bounded adaptive tessellation of displacement maps

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Graphic Interface 2002

作者： Moule, Kevin McCool, Michael D. Computer Graphics Lab Department of Computer Science University of Waterloo Waterloo Ont. Canada

Displacement mapping is a technique for applying fine geometric detail to a simpler base surface. The displacement is often specified as a scalar function which makes it relatively easy to increase visual complexity without the difficulties inherent in more general modeling techniques. We would like to use displacement mapping in real-time applications. Ideally, a graphics accelerator should create a polygonal tessellation of the displaced surface on the fly to avoid storage and host bandwidth overheads. We present an online, adaptive, crack-free tessellation scheme for real-time displacement mapping that uses only local information for each triangle to perform a view-dependent tessellation. The tessellation works in homogeneous coordinates and avoids re-transformation of displaced points, making it suitable for high-performance hardware implementation. The use of interval analysis produces meshes with good error bounds that converge quickly to the true surface.

关键词： computer graphics

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Motion competition: Variational integration of motion segmentation and shape regularization

Motion competition: Variational integration of motion segmen...

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24th German Association for Pattern Recognition Symposium, DAGM 2002

作者： Cremers, Daniel Schnörr, Christoph Computer Vision Graphics and Pattern Recognition Group Department of Mathematics and Computer Science University of Mannheim MannheimD–68131 Germany

ISBN: (纸本)354044209X

We present a variational method for the segmentation of piecewise affine flow fields. Compared to other approaches to motion segmentation, we minimize a single energy functional both with respect to the affine motion models in the separate regions and with respect to the shape of the separating contour. In the manner of region competition, the evolution of the segmenting contour is driven by a force which aims at maximizing a homogeneity measure with respect to the estimated motion in the adjoining regions. We compare segmentations obtained for the models of piecewise affine motion, piecewise constant motion, and piecewise constant intensity. For objects which cannot be discriminated from the background by their appearance, the desired motion segmentation is obtained, although the corresponding segmentation based on image intensities fails. The region– based formulation facilitates convergence of the contour from its initialization over fairly large distances, and the estimated discontinuous flow field is progressively improved during the gradient descent minimization. By including in the variational method a statistical shape prior, the contour evolution is restricted to a subspace of familiar shapes, such that a robust estimation of irregularly moving shapes becomes feasible. © Springer-Verlag Berlin Heidelberg 2002.

关键词： Flow fields

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Spatialized audio rendering for immersive virtual environments 02

Spatialized audio rendering for immersive virtual environmen...

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Proceedings of the ACM Symposium on Virtual Reality Software and Technology

作者： Naef, Martin Staadt, Oliver Gross, Markus Computer Graphics Laboratory ETH Zurich Zurich Switzerland Computer Science Department University of California Davis Davis CA United States

ISBN: (纸本)9781581135305

We present a spatialized audio rendering system for the use in immersive virtual environments. The system is optimized for rendering a sufficient number of dynamically moving sound sources in multi-speaker environments using off-the-shelf audio hardware. Based on simplified physics-based models, we achieve a good trade-off between audio quality, spatial precision, and performance. Convincing acoustic room simulation is accomplished by integrating standard hardware reverberation devices as used in the professional audio and broadcast community. We elaborate on important design principles for audio rendering as well as on practical implementation issues. Moreover, we describe the integration of the audio rendering pipeline into a scene graph-based virtual reality toolkit.

关键词： Virtual reality

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Designing 3-D nonlinear diffusion filters for high performance cluster computing

Designing 3-D nonlinear diffusion filters for high performan...

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24th German Association for Pattern Recognition Symposium, DAGM 2002

作者： Bruhn, Andrés Jakob, Tobias Fischer, Markus Kohlberger, Timo Weickert, Joachim Brüning, Ulrich Schnörr, Christoph Mathematical Image Analysis Group Mathematics and Computer Science Saarland University Building 27.1 Saarbrücken66041 Germany Computer Architecture Group Department of Mathematics and Computer Science University of Mannheim Mannheim68131 Germany Computer Vision Graphics and Pattern Recognition Group Department of Mathematics and Computer Science University of Mannheim Mannheim68131 Germany

ISBN: (纸本)354044209X

This paper deals with parallelization and implementation aspects of PDE based image processing models for large cluster environments with distributed memory. As an example we focus on nonlinear isotropic diffusion filtering which we discretize by means of an additive operator splitting (AOS). We start by decomposing the algorithm into small modules that shall be parallelized separately. For this purpose image partitioning strategies are discussed and their impact on the communication pattern and volume is analyzed. Based on the results we develop an algorithmic implementation with excellent scaling properties on massively connected low latency networks. Test runs on a high–end Myrinet cluster yield almost linear speedup factors up to 209 for 256 processors. This results in typical denoising times of 0.5 seconds for five iterations on a 256 × 256 × 128 data cube. © Springer-Verlag Berlin Heidelberg 2002.

关键词： Cluster computing

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Combining the advantages of local and global optic flow methods

Combining the advantages of local and global optic flow meth...

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24th Symposium of the German Pattern Recognition Association, DAGM 2002

作者： Bruhn, Andres Weickert, Joachim Schnorr, Christoph Mathematical Image Analysis Group Faculty of Mathematics and Computer Science Saarland University 66041 Saarbrücken Germany Computer Vision Graphics and Pattern Recognition Group Department of Mathematics and Computer Science University of Mannheim 68131 Mannheim Germany

ISBN: (纸本)354044209X

Differential methods are frequently used techniques for optic flow computations. They can be classified into local methods such as the Lucas-Kanade technique or Bigün's structure tensor method, and into global methods such as the Horn-Schunck approach and its modifications. Local methods are known to be more robust under noise, while global techniques yield 100% dense flow fields. No clear attempts to combine the advantages of these two classes of methods have been made in the literature so far. This problem is addressed in our paper. First we juxtapose the role of smoothing processes that are required in local and global differential methods for optic flow computation. This discussion motivates us to introduce and evaluate a novel method that combines the advantages of local and global approaches: It yields dense flow fields that are robust against noise. Finally experiments with different sequences are performed demonstrating its excellent results. © Springer-Verlag Berlin Heidelberg 2002.

关键词： Flow fields

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INVISIP: Usage of information visualization techniques to access geospatial data archives 13th

INVISIP: Usage of information visualization techniques to ac...

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13th International Conference on Database and Expert Systems Applications, DEXA 2002

作者： Göbel, Stefan Haist, Jörg Reiterer, Harald Müller, Frank Fraunhofer Institute for Computer Graphics GIS department Fraunhoferstr. 5 Darmstadt64283 Germany University of Konstanz Department of Computer & Information Science Universitätsstr 10 Konstanz78457 Germany

ISBN: (纸本)3540441263

Complex application examples or scenarios such as site planning need a lot of information, especially spatially referenced data1 in order to find a best place for a new building or an industrial area and to solve individual planning tasks such as generating ecological, environmental or traffic reports. Recent initiatives to geospatial data archives offer access to a wealth of distributed data covered by the widespread information spectrum of different geodata disciplines (e.g. environmental data, geologic data, cadastral data, remote sensing data or socio-demographic data), but offer only basic levels of interactivity and user assistance. The EU-funded project INVISIP (Information Visualization in Site Planning, IST-2000-29640) addresses this lack of usability and aims to develop new concepts and methods to support all involved parties within the different phases of the multi-step site planning process. This paper describes INVISIP and introduces GeoCrystal and SuperTable as new information visualization techniques to support users in this process. © Springer-Verlag Berlin Heidelberg 2002.

关键词： Visualization

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Modified marching octahedra for optimal regular meshes 02

Modified marching octahedra for optimal regular meshes

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International Conference on computer graphics and Interactive Techniques, SIGGRAPH 2002

作者： Carr, Hamish Theußl, Thomas Moller, Torsten Department of Computer Science University of British Columbia VancouverBC Canada Institute of Computer Graphics and Algorithms Vienna University of Technology VancouverBC Austria Department of Computing Science Simon Fraser University VancouverBC Canada

ISBN: (纸本)1581135254

Theußl et al. [Theußl et al. 2001] showed that volumetric data sampled on a body-centred cubic (BCC) lattice is nearly 30% more efficient than data sampled on a cubic lattice, and produced volume renderings using splatting. We extend this work to generate isosurfaces based on the BCC lattice, and also on the hexagonal-close packed (HCP) grid. This sketch presents a modified version of marching octahedra that simplifies the BCC mesh to an octahedral mesh to reduce the number of triangles generated for the isosurface.

关键词： Volume rendering

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Novel uses of Pinch Gloves™ for virtual environment interaction techniques

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Virtual Reality 2002年第3期6卷 122-129页

作者： Bowman, D.A. Wingrave, C.A. Campbell, J.M. Ly, V.Q. Rhoton, C.J. Department of Computer Science Virginia Tech. Blacksburg VA United States College of Computing Graphics Visualization and Usability Center Georgia Institute of Technology GA United States Department of Computer Science (0106) Virginia Tech. Blacksburg VA 24061 United States

The usability of three-dimensional (3D) interaction techniques depends upon both the interface software and the physical devices used. However, little research has addressed the issue of mapping 3D input devices to interaction techniques and applications. This is especially crucial in the field of Virtual Environments (VEs), where there exists a wide range of potential 3D input devices. In this paper, we discuss the use of Pinch Gloves™ - gloves that report contact between two or more fingers - as input devices for VE systems. We begin with an analysis of the advantages and disadvantages of the gloves as a 3D input device. Next, we present a broad overview of three novel interaction techniques we have developed using the gloves, including a menu system, a text input technique, and a two-handed navigation technique. All three of these techniques have been evaluated for both usability and task performance. Finally, we speculate on further uses for the gloves. © Springer-Verlag London Ltd.

关键词： 3D Input Devices Interaction Techniques Pinch Gloves Usability Evaluation Virtual Environments

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Using perceptual texture masking for efficient image synthesis

Using perceptual texture masking for efficient image synthes...

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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

关键词： Image compression

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