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19th brazilian symposium on computer graphics and image processing (sibgrapi 2006)

作者： Gedeon, Tomas Arathorn, David Montana State Univ Dept Math Sci Bozeman MT 59715 USA Montana State Univ Gen Intelligence Corp Ctr Computat Biol Bozeman MT 59715 USA

the map-seeking circuit (MSC) is an explicit biologically-motivated computational mechanism which provides practical solution of problems in object recognition, image registration and stabilization, limb inverse-kinematics and other inverse problems which involve transformation discovery. We formulate this algorithm as discrete dynamical system on a set Delta = Pi(L)(l=1)Delta((l)), where each Delta((l)) is a compact subset of a nonnegative orthant of R-n, and show that for an open and dense set of initial conditions in Delta the corresponding solutions converge to either a vector with unique nonzero element in each Delta((l)) or to a zero vector. the first result implies that the circuit finds a unique best mapping which relates reference pattern to a target pattern;the second result is interpreted as "no match found". these results verify numerically observed behavior in numerous practical applications.

关键词： map seeking circuits computer vision dynamical systems Lyapunov function

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Generalized rigid and generalized affine image registration and interpolation by geometric multigrid

Generalized rigid and generalized affine image registration ...

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19th brazilian symposium on computer graphics and image processing (sibgrapi 2006)

作者： Keeling, Stephen L. Karl Franzens Univ Graz Inst Math & Wissenschaftliches Rechmen A-8010 Graz Austria

Generalized rigid and generalized affine registration and interpolation obtained by finite displacements and by optical flow are here developed variationally and numerically as well as with respect to a geometric multigrid solution process. For high order optimality systems under natural boundary conditions, it is shown that the convergence criteria of Hackbusch (Iterative Solution of Large Sparse Systems of Equations. Springer, Berlin, 1993) are met. Specifically, the Galerkin formalism is used together with a multi-colored ordering of unknowns to permit vectorization of a symmetric successive over-relaxation on image processing systems. the geometric multigrid procedure is situated as an inner iteration within an outer Newton or lagged diffusivity iteration, which in turn is embedded within a pyramidal scheme that initializes each outer iteration from predictions obtained on coarser levels. Differences between results obtainable by finite displacements and by optical flows are elucidated. Specifically, independence of image order can be shown for optical flow but in general not for finite displacements. Also, while autonomous optical flows are used in practice, it is shown explicitly that finite displacements generate a broader class of registrations. this work is motivated by applications in histological reconstruction and in dynamic medical imaging, and results are shown for such realistic examples.

关键词： generalized rigid generalized affine image registration image interpolation geometric multigrid

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AFRIGRAPH: computer graphics in Africa

AFRIGRAPH: Computer graphics in Africa

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18th brazilian symposium on computer graphics and image processing (sibgrapi 2005)

作者： Gain, J. E. Strasser, W. Univ Cape Town Collaborat Visual Comp Lab ZA-7925 Cape Town South Africa Univ Tubingen Wilhelm Schickard Inst Informat Graph Interakt Sy D-7400 Tubingen Germany

Afrigraph is an organization whose purpose is to help consolidate and promote the practice of relevant computer graphics in Africa in academia, the arts and industry. It was formed as a result of ACM SIGGRAPH initiatives beginning in 2000 and culminating in it being constituted as a professional body complete with a constitution modeled on that of ACM SIGGRAPH. the mandate of the organization also includes local issues such as the digital divide, curriculum design and intellectual property affecting growth and development of computer graphics in Africa. the papers and tutorials of the conferences have been wide-ranging including digital reconstruction of African art works, relighting of archaeological sites and automated sign language translation. Topics in Virtual Reality, computer graphics, Visualization and Interaction have also been well represented.

关键词： computer graphics

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Segmenting White Matter Hyperintensity in Alzheimer's Disease using U-Net CNNs 35

Segmenting White Matter Hyperintensity in Alzheimer's Diseas...

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35th sibgrapi Conference on graphics, Patterns and images (sibgrapi)

作者： Duarte, Kaue T. N. Gobbi, David G. Sidhu, Abhijot S. McCreary, Cheryl R. Saad, Feryal Das, Nita Smith, Eric E. Frayne, Richard Univ Calgary Hotchkiss Brain Inst Radiol & Clin Neurosci Calgary AB T2N IN4 Canada Foothills Med Ctr Calgary Image Proc & Anal Ctr Calgary AB T2N 2T9 Canada Univ Calgary Biomed Engn Grad Program Calgary AB T2N IN4 Canada Foothills Med Ctr Seaman Family MR Res Ctr Calgary AB T2N 2T9 Canada

ISBN: (数字)9781665453851

ISBN: (纸本)9781665453851

White-matter hyperintensity (WMH) is associated with many disorders where it is suggestive of underlying cerebrovascular, small-vessel disease pathology. However, its role in Alzheimer's disease (AD), mixed, and vascular dementia remains an open area of research. the fluid-attenuated inversion recovery (FLAIR) magnetic resonance (MR) imaging sequence is commonly used to visualize WMH because it provides good image contrast, not only between WMH and normal tissue, but also between WMH and cerebrospinal fluid. Manual segmentation of WMH lesions in brain volumes, on a slice-by-slice basis, is time-consuming with high inter-rater variability, however, this process remains the broadly accepted gold standard. In this study, variations of 2D, 2.5D and 3D U-shaped convolutional neural networks (U-Net CNNs) were used to perform semantic segmentation on FLAIR images. We evaluated these models in brain volumes obtained from 186 individuals from one of three disease classes: healthy normal (N = 94), mild cognitive impairment (N = 55), and AD (N = 37). Four common architectures (VGG16, VGG19, ResNet and EfficientNetB0) were employed as feature extractors. Results were assessed across the whole brain and by brain region (frontal, occipital, parietal, temporal lobes plus the insula) to identify differences in performance. In general, the predicted WMH volumes had an F-measure score >95% on the test data compared to manual segmentation. this work identified that 2.5D with either VGG16 or VGG19 was the most suitable configuration when segmenting WMH. WMH segmentation performance and measured volume was found to vary between regions and disease classes. U-Net CNN architectures have good performance and may provide valuable insights about the white matter pathology.

关键词： Training Pathology Volume measurement Manuals Brain modeling Feature extraction Convolutional neural networks

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XIX brazilian symposium on computer graphics and image processing - Copyright

XIX Brazilian Symposium on Computer Graphics and Image Proce...

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brazilian symposium on computer graphics and image processing (sibgrapi)

Copyright and Reprint Permissions: Abstracting is permitted with credit to the source. Libraries may photocopy beyond the limits of US copyright law, for private use of patrons, those articles in this volume that carry a code at the bottom of the first page, provided that the per-copy fee indicated in the code is paid through the Copyright Clearance Center. the papers in this book comprise the proceedings of the meeting mentioned on the cover and title page. they reflect the authors' opinions and, in the interests of timely dissemination, are published as presented and without change. their inclusion in this publication does not necessarily constitute endorsement by the editors or the Institute of Electrical and Electronics Engineers, Inc.

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Mumford-Shah on the move: Region-based segmentation on deforming manifolds with application to 3-D reconstruction of shape and appearance from multi-view images

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JOURNAL OF MAthEMATICAL IMAGING AND VISION 2007年第2-3期29卷 219-234页

作者： Jin, Hailin Yezzi, Anthony J. Soatto, Stefano Adobe Syst Inc Off Tech San Jose CA 95110 USA Georgia Inst Technol Sch Elect & Comp Engn Atlanta GA 30332 USA Univ Calif Los Angeles Dept Comp Sci Los Angeles CA 90025 USA

We address the problem of estimating the shape and appearance of a scene made of smooth Lambertian surfaces with piecewise smooth albedo. We allow the scene to have self-occlusions and multiple connected components. this class of surfaces is often used as an approximation of scenes populated by man-made objects. We assume we are given a number of images taken from different vantage points. Mathematically this problem can be posed as an extension of Mumford and Shah's approach to static image segmentation to the segmentation of a function defined on a deforming surface. We propose an iterative procedure to minimize a global cost functional that combines geometric priors on both the shape of the scene and the boundary between smooth albedo regions. We carry out the numerical implementation in the level set framework.

关键词： variational methods Mumford-Shah functional image segmentation multi-view stereo level set methods curve evolution on surfaces dense shape reconstruction structure from motion visibility

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Plausible image Based Soft Shadows Using Occlusion Textures

Plausible Image Based Soft Shadows Using Occlusion Textures

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brazilian symposium on computer graphics and image processing (sibgrapi)

作者： Elmar Eisemann Xavier Decoret ARTIS-GRAVIR IMAG-INRIA France

this paper presents a novel image-based approach to render plausible soft shadows for complex dynamic scenes with rectangular light sources. the algorithm's performance is mostly independent of the scene complexity and the source's size. Occluders and receivers do not need to be separated and no knowledge about the scene representation is required, making the method easy to use. the main idea is to approximate the occlusion in the scene with pre-filtered occlusion textures. the visibility of the light source at a point in space is estimated by accumulating the occlusion caused by each texture, using a novel formula based on probabilities

关键词： Layout Light sources Rendering (computer graphics) computer graphics Runtime Hardware image coding Shadow mapping Filtering Statistics

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Hardware-assisted Rendering of CSG Models

Hardware-assisted Rendering of CSG Models

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brazilian symposium on computer graphics and image processing (sibgrapi)

作者： Fabiano Romeiro Luiz Velho Luiz Henrique De Figueiredo Harvard University USA IMPA Brazil

Current methods that interactively render reasonably complex CSG objects are image based and are severely bandwidth limited. this paper presents a new approach to ray-tracing CSG objects composed of convex primitives that combines spatial subdivision and ray-tracing methods. By performing spatial subdivision on the CSG object until locally it is simple enough to be rendered effectively and efficiently on a GPU, we are able to share the load more evenly between the CPU and the GPU and depend less on bandwidth and more on GPU instruction throughput than current methods, hence obtaining better scalability with newer hardware

关键词： Rendering (computer graphics) Hardware Bandwidth throughput computer graphics Ray tracing Scalability Solid modeling Process design image converters

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A computer-Assisted Colorization Algorithm based on Topological Difference

A Computer-Assisted Colorization Algorithm based on Topologi...

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brazilian symposium on computer graphics and image processing (sibgrapi)

作者： Hedlena Bezerra Bruno Feijo Luiz Velho Pontifícia Universidade Católica do Rio de Janeiro France ARTIS/GRAVIR/IMAG-INRIA France IMPA-Instituto de Matemática Pura e Aplicada Brazil ARTIS/GRAVIR/IMAG-INRIA Brazil

Region-based approaches to cel painting typically use shape similarity and topology relations between regions of consecutive animation frames. this paper presents a new colorization algorithm based on topological differences defined over a hierarchical graph of adjacent regions, which allows an almost full automatic colorization process. Also this paper discusses other attributes that improve the solution of the image association problem

关键词： Shape Painting Topology Pipelines Facial animation Inverse problems Interpolation image analysis Performance analysis computer graphics

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Physically based deformable models in computer graphics

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computer graphics FORUM 2006年第4期25卷 809-836页

作者： Nealen, Andrew Mueller, Matthias Keiser, Richard Boxerman, Eddy Carlson, Mark Tech Univ Berlin Berlin Germany ETH Comp Graph Lab Zurich Switzerland Ubisoft Montreal Montreal PQ Canada

physically based deformable models have been widely embraced by the computer graphics community. Many problems outlined in a previous survey by Gibson and Mirtich have been addressed, thereby making these models interesting and useful for both offline and real-time applications, such as motion pictures and video games. In this paper, we present the most significant contributions of the past decade, which produce such impressive and perceivably realistic animations and simulations: finite element/difference/volume methods, mass-spring systems, mesh-free methods, coupled particle systems and reduced deformable models-based on modal analysis. For completeness, we also make a connection to the simulation of other continua, such as fluids, gases and melting objects. Since time integration is inherent to all simulated phenomena, the general notion of time discretization is treated separately, while specifics are left to the respective models. Finally, we discuss areas of application, such as elastoplastic deformation and fracture, cloth and hair animation, virtual surgery simulation, interactive entertainment and fluid/smoke animation, and also suggest areas for future research.

关键词： physically based animation deformation continuum elasticity time integration FEM mass-spring mesh-free methods modal analysis fluid animation

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