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brazilian symposium on computer graphics and image processing (SIBGRAPI)

作者： R. Farias J.S.B. Mitchell C.T. Silva B. Wylie Dept. of Appl. Math. & Stat. State Univ. of New York Stony Brook NY USA Department of Applied Mathematics and Statistics State University of New York Stony Brook Stony Brook NY USA AT and T Research Laboratories Florham Park NJ USA

Many papers have presented rendering techniques and simplification ideas with the objective of speeding up image generation for irregular grid data sets. For large data sets, however, even the current fastest algorithms are known to require seconds to generate each image, making real time analysis of such data sets very difficult, or even impossible, unless one has access to powerful and expensive computer hardware. In order to synthesize a system for handling very large data set analysis, we have assembled algorithms for rendering, simplification and triangulation, and added to them some optimizations. We have made some improvements on one of the best current algorithms for rendering irregular grids, and added to it some simple approximation methods in both image and object space, resulting in a system that achieves high frame rates, even on slow computers without any specific graphic hardware. The algorithm adapts itself to the time budget it has available for each image generation, using hierarchical representations of the mesh for faster delivery of images when transformations are imposed to the data. When given additional time, the algorithm generates finer images, obtaining the precise final image if given sufficient time. We were able to obtain frame rates of the order of 5 Hz for medium-sized data sets, which is about 20 times faster than previous rendering algorithms. With a trade-off between image accuracy and speed, similar frame rates can be achieved on different computers.

关键词： Time factors Rendering (computer graphics) image generation Data analysis Algorithm design and analysis Hardware Power generation image analysis Assembly systems Approximation algorithms

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Directional analysis of images with Gabor wavelets

Directional analysis of images with Gabor wavelets

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brazilian symposium on computer graphics and image processing (SIBGRAPI)

作者： R.M. Rangayyan R.J. Ferrari J.E.L. Desautels A.F. Frere Department of Electrical and Computer Engineering University of Calgary Alberta Canada Department of Electrical Engineering University of São Paulo Sao Carlos SP Brazil Alberta Cancer Board Alberta Canada Nucleus of Science and Technology University of Mogi das Cruzes Mogi das Cruzes SP Brazil

The paper presents a new scheme for analysis of linear directional components in images by using a multiresolution representation based on Gabor wavelets. A dictionary of Gabor filters with varying tuning frequency and orientation, specifically designed in order to reduce the redundancy in the wavelet-based representation, is applied to the given image. The filter responses for different scales and orientation are analyzed by using the Karhunen-Loeve (KL) transform and Otsu's (1979) method of thresholding. The KL transform is applied to select the principal components of the filter responses, preserving only the most relevant directional elements appearing at all scales. The first N principal components, thresholded by using Otsu's method, are used to reconstruct the magnitude and phase of the directional components of the image. Rose diagrams computed from the phase images are used for quantitative and qualitative analysis of the oriented patterns. The proposed scheme is applied to the analysis of asymmetry between left and right mammograms. For this purpose, a set of three features is extracted from the Rose diagrams and used in a parametric statistical classifier. A total of 80 images from 20 normal cases, 14 asymmetric cases, and 6 distortion cases from the Mini-MIAS database were used to evaluate the scheme using the leave-one-out methodology, resulting in an average diagnostic accuracy of 72.5%.

关键词： image analysis Wavelet analysis Gabor filters Karhunen-Loeve transforms image resolution Dictionaries Tuning Frequency image reconstruction Pattern analysis

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Target search by bottom-up and top-down fuzzy information

Target search by bottom-up and top-down fuzzy information

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brazilian symposium on computer graphics and image processing (SIBGRAPI)

作者： E.M. de Almeida Neves J.E. Borelli A. Gonzaga Physics Institute at Sāo Carlos University of São Paulo Brazil School of Engineering at Sāo Carlos Department of Electrical Engineering University of São Paulo Sao Paulo Brazil

One of the basic tasks assigned to the attentional mechanism is to decide which location in the visual field we must pay attention first. An object containing a distinctive feature can attract attention in a bottom-up way. By comparing one object with the others present in the scene, bottom-up conspicuity features are used to guide attention to the most different object. Top-down hints are based on the previous knowledge about the objects or on which features are important to locate them and also have a large influence on the attended locations. Inspired by the mechanisms of human visual attention we developed a new methodology to integrate bottom-up and top-down information by using a fuzzy net containing three fuzzy subsystems. The first bottom-up subsystem allow us to combine features and infer with great flexibility some intuitive decision rules based on the visual perception principles such as the Gestalt laws. The second top-down subsystem combines different features according to the relevance of them in different tasks. Finally, the last subsystem integrates the information of the previous systems and gives a general salience index. The new methodology was tested in geometrical objects considering the features that attract attention to human beings.

关键词： Humans Layout Visual perception Interference Physics Testing Psychology Retina Information processing

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Fast perception-based depth of field rendering 00

Fast perception-based depth of field rendering

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2000 ACM symposium on Virtual Reality Software and Technology, VRST 2000

作者： Mulder, Jurriaan D. Van Liere, Robert Center for Mathematics and Computer Science Kruislaan 413 Amsterdam1098 SJ Netherlands

ISBN: (纸本)1581133162

Current algorithms to create depth of field (DOF) effects are either too costly to be applied in VII, systems, or they produce inaccurate results. In this paper, we present a new algorithm to create DOF effects. The algorithm is based on two techniques: one of high accuracy and one of high speed but less accurate. The latter is used to create DOF effects in the peripheral viewing area where accurate results are not necessary. The first is applied to the viewing volume focussed at by the viewer. Both techniques make extensive use of rendering hardware, for texturing as well as image processing. The algorithm presented in this paper is an improvement over other (fast) DOF algorithms in that it is faster and provides better quality DOF effects where it matters most. © ACM 2000.

关键词： Virtual reality

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Digital visual information processing: adding vision and graphics

Digital visual information processing: adding vision and gra...

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International symposium on image and Signal processing and Analysis

作者： F.W. Leberl Institute for Computer Graphics and Vision Graz University of Technology Graz Austria

ISBN: (纸本)9539676924

Models of the real world are at least 3-dimensional and require the technologies of image processing and computer graphics. We see the processing of images, be they of the real world or of models in a computer, as one and the same basic technology, namely "digital visual information processing". This paper seeks to illustrate and justify this point-of-view by means of examples taken mostly from the work at the author's institute.

关键词： Information processing computer graphics Rendering (computer graphics) Pipelines computer vision Signal processing image analysis Signal analysis image sequence analysis image texture analysis

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A hybrid method of image synthesis in IBR for novel viewpoints 00

A hybrid method of image synthesis in IBR for novel viewpoin...

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2000 ACM symposium on Virtual Reality Software and Technology, VRST 2000

作者： Liu, Xuehui Sun, Hanqiu Wu, Enhua Lab. of Computer Science Institute of Software Chinese Academy of Sciences P.O.Box 8718 Beijing100080 China Dep. of Comp. Scie. and Eng. Chinese University of Hong Kong Shatin N.T. Hong Kong Faculty of Science and Technology University of Macao China

ISBN: (纸本)1581133162

Due to visibility change and surface enlargement in producing a novel view from a new viewpoint, 3D re-projection from one reference image in IBMR inevitably produces holes in the destination image. Even worse, exposure errors occur when a background region occluded is visible in a desired image because of the absence of some background elements in the reference image. The general solution to this kind of problems is to use multiple images from different viewpoints as input source. By doing so however, the rendering cost would increase with the number of reference images and the composition algorithm has to rely on the z-buffer processing. In fact, plenty of redundant information exists among different reference images. Seeking for a nice way to extract the information needed in the novel view from the reference images is the key issue in solving the problem. In this paper, we propose a new method of image synthesis from multiple reference images. The method combines forward warping and backward warping to fulfil the image composition task for a novel viewpoint. The primary inspiration behind the development of our image synthesis method comes from a fact that the polygon edge geometry may indicate where an exposure and, possible an exposure error occur in the destination image if object silhouettes are prior known. The feature that intersection between scanline and polygons must be in pairs is employed to distinguish holes caused by enlargement of surfaces from those by visibility change. Different heuristic methods are used m choose one image as a primary reference image which shares the most resemblance with the destination image, and other reference images for filling different kinds of holes. Depth continuity along scanline and the depth information already present in the destination image are employed to accelerate the searching process of the corresponding pixels for filling holes. © ACM 2000.

关键词： Visibility

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Real time, accurate, multi-featured rendering of bump mapped surfaces

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computer graphics FORUM 2000年第3期19卷 C119-+页

作者： Tarini, M Cignoni, P Rocchini, C Scopigno, R CNR Ist Elaborazione Informaz I-56126 Pisa Italy

We present a new technique to render in real time objects which have part of their high frequency geometric detail encoded in bump maps. It is based on the quantization of normal-maps, and achieves excellent result both in rendering time and rendering quality, with respect to other alternative methods. The method proposed also allows to add many interesting visual effects, even for object with large bumb maps, including non-s rendering, chrome effects, shading under multiple lights, rendering of different materials within a single object, specular reflections and others. Moreover, the implementation of the method is not complex and can be eased by software reuse.

关键词： MAPPINGS (Mathematics) computer graphics DIGITAL image processing computer simulation

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Floating points: A method for computing stipple drawings

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computer graphics FORUM 2000年第3期19卷 C41-C50页

作者： Deussen, O Hiller, S van Overveld, C Strothotte, T Univ Magdeburg Fac Comp Sci D-39106 Magdeburg Germany Eindhoven Univ Technol Dept Math & Comp Sci NL-5600 MB Eindhoven Netherlands

We present a method for computer generated pen-and-ink illustrations by the simulation of stippling. In a stipple drawing, dots are used to represent tone and also material of surfaces. We create such drawings by generating an initial dot set which is then processed by a relaxation method based on Voronoi diagrams. The point patterns generated are approximations of Poisson disc distributions and can also be used for integrating functions or the positioning of objects. We provide an editor similar to paint systems for interactively creating stipple drawings. This makes it possible to create such drawings within a matter of hours, instead of days or even weeks when the drawing is done manually.

关键词： computer drawing computer simulation Stipple engraving image processing

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Automatic surface reconstruction from point sets in space

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computer graphics FORUM 2000年第3期19卷 C457-C465页

作者： Attene, M Spagnuolo, M CNR Ist Matemat Appl I-16132 Genoa Italy

In this paper an algorithm is proposed that takes as input a generic set of unorganized points, sampled on a real object, and returns a closed interpolating surface. Specifically, this method generates a closed 2-manifold surface made of triangular faces, without limitations on the shape or genus of the original solid. The reconstruction method is based on generation of the Delaunay tetrahedralization of the point set, followed by a sculpturing process constrained to particular criteria. The main applications of this tool are in medical analysis and in reverse engineering areas. It is possible, for example, to reconstruct anatomical parts starting from surveys based on TACs or magnetic resonance.

关键词： ALGORITHMS TETRAHEDRA DIGITAL image processing TOPOLOGY

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image layer decomposition for distributed real-time rendering on clusters

Image layer decomposition for distributed real-time renderin...

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International symposium on Parallel and Distributed processing (IPDPS)

作者： T.D. Nguyen J. Zahorjan Department of Computer Science Rutgers University Piscataway NJ USA Department of Computer Science and Engineering University of Washington Seattle WA USA

We propose a novel work partitioning technique, image layer decomposition (ILD), designed specifically to support distributed real-time rendering on commodity clusters. ILD has several advantages over previous partitioning algorithms for our targeted environment, including its compatibility with the use of hardware graphics accelerators, decoupling of communication bandwidth requirement from scene complexity, and reduced communication bandwidth growth as the system size increases. Furthermore, ILD tries to optimize the rendering of a sequence of frames (of an interactive application) instead of only individual frames. We simulate ILD using traces taken from a VRML viewer Our results show that ILD can be expected to work well up to moderately sized clusters and to outperform sort-last, a common partitioning approach, because of its smaller communication bandwidth requirement.

关键词： Rendering (computer graphics) Bandwidth Layout Electrical capacitance tomography Read only memory Hardware computer science Workstations Personal communication networks Costs

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