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5th International Symposium on Virtual Reality, Archaeology and Intelligent Cultural Heritage, VAST 2004

作者： Bendels, Gerhard Heinrich Degener, Patrick Wahl, Roland Körtgen, Marcel Klein, Reinhard Institute for Computer Science II Computer Graphics University of Bonn Germany

ISBN: (纸本)3905673185

Digitizing real-life objects via range scanners, stereo vision or tactile sensors usually requires the composition of multiple range images. In this paper we exploit intensity images often recorded with the range data and propose a fully automatic registration technique using 2D-image features with intrinsic scale information for finding corresponding points on the 3D-views. In our approach, the fine registration of two range images is performed by first aligning the feature points themselves, followed by a so-called constrained-domain alignment step. In the latter, rather than feature points, we consider feature surface elements that are derived using the scale information inherently established with the 2D-features. The global registration error is minimized using graph relaxation techniques to mediate the transformations required to align the multiple range images. We demonstrate the power and feasibility of our method by a case-study in the cultural heritage domain. © The Eurographics Association 2004.

关键词： Stereo image processing

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A TWO-SIZE WRIGHT-FISHER MODEL: ASYMPTOTIC ANALYSIS VIA UNIFORM RENEWAL THEORY

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arXiv 2025年

作者： Alsmeyer, Gerold Cordero, Fernando Dopmeyer, Hannah Institute for Mathematical Stochastics Department of Mathematics and Computer Science University of Münster Orleans-Ring 10 Münster48149 Germany Institute of Mathematics BOKU University Gregor-Mendel-Straße 33/II Vienna1180 Austria Faculty of Technology Bielefeld University Box 100131 Bielefeld33501 Germany

MSC Codes Primary: 60K05, 92D25, Secondary: 60K10, 60K35, 60J70We consider a population with two types of individuals, distinguished by the resources required for reproduction: type-0 (small) individuals need a fractional resource unit of size ϑ ∈ (0, 1), while type-1 (large) individuals require 1 unit. The total available resource per generation is R. To form a new generation, individuals are sampled one by one, and if enough resources remain, they reproduce, adding their offspring to the next generation. The probability of sampling an individual whose offspring is small is ρR(x), where x is the proportion of small individuals in the current generation. This discrete-time stochastic model is called the two-size Wright-Fisher model, where the function ρR can represent mutation and/or frequency-dependent selection. We show that on the evolutionary time scale, i.e. accelerating time by a factor R, the frequency process of type-0 individuals converges to the solution of a Wright-Fisher-type SDE. The drift term of that SDE accounts for the bias introduced by the function ρR and the consumption strategy, the latter also inducing an additional multiplicative factor in the diffusion term. To prove this, the dynamics within each generation are viewed as a renewal process, with the population size corresponding to the first passage time τ(R) above level R. The proof relies on methods from renewal theory, in particular a uniform version of Blackwell’s renewal theorem for binary, non-arithmetic random variables, established via Ε-coupling. Copyright © 2025, The Authors. All rights reserved.

关键词： Stochastic systems

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Real-time appearance preserving out-of-core rendering with shadows

Real-time appearance preserving out-of-core rendering with s...

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15th Eurographics Workshop on Rendering Techniques, EGSR 2004

作者： Guthe, Michael Borodin, Pavel Balázs, Ákos Klein, Reinhard Institute of Computer Science II Computer Graphics Group University of Bonn Germany

ISBN: (纸本)3905673126

Despite recent advances in finding efficient LOD-representations for gigantic 3D objects, rendering of complex, gigabyte-sized models and environments is still a challenging task, especially under real-time constraints and high demands on the visual accuracy. The two general approaches are using either a polygon- or a point-based representation for the simplified geometry. With the polygon-based approaches high frame rates can be achieved by sacrificing the exact appearance and thus the image quality. Point-based approaches on the other hand preserve higher image quality at the cost of higher primitive counts and therefore lower frame rates. In this paper we present a new hybrid point-polygon LOD algorithm for real-time rendering of complex models and environments including shadows. While rendering different LODs, we preserve the appearance of an object by using a novel error measure for simplification which allows us to steer the LOD generation in such a way that the geometric as well as the appearance deviation is bounded in image space. Additionally, to enhance the perception of the models shadows should be used. We present a novel LOD selection and prefetching method for real-time rendering of hard shadows. In contrast to the only currently available method for out-of-core shadow generation, our approach entirely runs on a single CPU system. © The Eurographics Association 2004.

关键词： Image quality

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Free-Form Deformation with Rational DMS-Spline Volumes

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Journal of computer science & Technology 2008年第5期23卷 862-873页

作者：徐岗汪国昭陈小雕 Institute of Computer Graphics and Image Processing Zhejiang University Department of Mathematics Zhejiang University College of Computer Science Hangzhou Dianzi University INRIA Nancy France

In this paper, we propose a novel free-form deformation （FFD） technique, RDMS-FFD （Rational DMS-FFD）, based on rational DMS-spline volumes. RDMS-FFD inherits some good properties of rational DMS-spline volumes and combines more deformation techniques than previous FFD methods in a consistent framework, such as local deformation, control lattice of arbitrary topology, smooth deformation, multiresolution deformation and direct manipulation of deformation. We first introduce the rational DMS-spline volume by directly generalizing the previous results related to DMS-splines. How to generate a tetrahedral domain that approximates the shape of the object to be deformed is also introduced in this paper. Unlike the traditional FFD techniques, we manipulate the vertices of the tetrahedral domain to achieve deformation results. Our system demonstrates that RDMS-FFD is powerful and intuitive in geometric modeling.

关键词： free-form deformation rational DMS-spline volume control lattice of arbitrary topology multiresolution deformation direct manipulation

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Interactive High Quality Trimmed NURBS Visualization Using Appearance Preserving Tessellation

Interactive High Quality Trimmed NURBS Visualization Using A...

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6th Joint Eurographics - IEEE TCVG Symposium on Visualization, VisSym 2004

作者： Guthe, M. Balázs, Á. Klein, R. Institute of Computer Science II Computer Graphics Bonn University Bonn Germany

ISBN: (纸本)390567307X

Trimmed NURBS models are the standard representation used in CAD/CAM systems and accurate visualization of large trimmed NURBS models at interactive frame rates is of great interest for industry. To visualize the quality of a surface several techniques like isophotes, reflection lines, etc. are used. Most existing approaches transform the NURBS surfaces into a fine polygonal representation and build static levels of detail from this representation. This polygonal approximation together with its normals are adjusted in a semi-automatic procedure to achieve the desired visual fidelity during visualization. Since this approach allows only for a fixed maximum accuracy and does not support deformable models, another more recent approach is to keep the NURBS representation and generate view-dependent LODs on the fly up to the currently required preciseness. However, so far this approach took only into account the geometric error of an approximation and thus neglected the various illumination artifacts introduced by the chosen (possibly view-dependent) triangulation. Although this problem can be solved by using normal maps, the resolution of the normal maps again limits the accuracy. Furthermore, the normal map generation requires a preprocessing step which prevents the support of deformable NURBS models. In this paper we present a novel automatic tessellation algorithm that considers the illumination artifacts and is well suited both for the generation of static and dynamic LOD schemes with guaranteed visual fidelity. Our new method is also capable of high quality visualization of further attributes like curvature, temperature, etc. on surfaces with little or no modification. © The Eurographics Association 2004.

关键词： Visualization

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Towards the next generation of 3D content creation 04

Towards the next generation of 3D content creation

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Working Conference on Advanced Visual Interfaces, AVI 2004

作者： Bendels, Gerhard H. Kahlesz, Ferenc Klein, Reinhard Inst. of Computer Science II Computer Graphics University of Bonn Germany

ISBN: (纸本)1581138679

In this paper we present a novel integrated 3D editing environment that combines recent advantages in various fields of computer graphics, such as shape modelling, video-based Human computer Interaction, force feedback and VR fine-manipulation techniques. This integration allows us to create a new compelling form of 3D object creation and manipulation preserving the metaphors designers, artists and painters have accustomed to during their day to day practice. Our system comprises a novel augmented reality workbench and enables users to simultaneously perform natural fine pose determination of the edited object with one hand and model or paint the object with the other hand. The hardware setup features a non-intrusive, video-based hand tracking subsystem, see-through glasses and a 3D 6-degree of freedom input device. The possibilities delivered by our AR workbench enable us to implement traditional and recent editing metaphors in an immersive and fully three-dimensional environment, as well as to develop novel approaches to 3D object interaction. © 2004 ACM.

关键词： Augmented reality

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PROBADO3D - Indexing and searching 3D CAD databases supporting planning through content-based indexing and 3D shape retrieval 10

PROBADO3D - Indexing and searching 3D CAD databases supporti...

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10th International Conference on Design and Decision Support Systems, DDSS 2010

作者： Blümel, Ina Berndt, René Ochmann, Sebastian Vock, Richard Wessel, Raoul German National Library of Science and Technology Hannover Germany Institute of Computer Graphics and Knowledge Visualization Graz University of Technology Austria Institute of Computer Science II Computer Graphics University of Bonn Germany

ISBN: (纸本)9789068141818

When modeling in 3D CAD, architects often search for already existing 3D content to complete their own design, e.g. environmental models, furniture models or detailed window profiles. 3D models are normally indexed and accessed based on textual metadata. As this metadata is expensive to obtain, PROBADO3D aims to develop workflows and tools for semi-automatic indexing of 3D models. Another goal is the development of intuitive visual search and presentation interfaces that face the needs of architects looking for 3D content. PROBADO3D is a part of the PROBADO framework designed to support multimedia objects of different domains.

关键词： Digital libraries

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Fusion of hyperspectral, multispectral, color and 3D point cloud information for the semantic interpretation of urban environments 4

Fusion of hyperspectral, multispectral, color and 3D point c...

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4th ISPRS Geospatial Week 2019

作者： Weinmann, M. Weinmann, M. Institute of Photogrammetry and Remote Sensing Karlsruhe Institute of Technology Germany Institute of Computer Science II-Computer Graphics University of Bonn Germany

In this paper, we address the semantic interpretation of urban environments on the basis of multi-modal data in the form of RGB color imagery, hyperspectral data and LiDAR data acquired from aerial sensor platforms. We extract radiometric features based on the given RGB color imagery and the given hyperspectral data, and we also consider different transformations to potentially better data representations. For the RGB color imagery, these are achieved via color invariants, normalization procedures or specific assumptions about the scene. For the hyperspectral data, we involve techniques for dimensionality reduction and feature selection as well as a transformation to multispectral Sentinel-2-like data of the same spatial resolution. Furthermore, we extract geometric features describing the local 3D structure from the given LiDAR data. The defined feature sets are provided separately and in different combinations as input to a Random Forest classifier. To assess the potential of the different feature sets and their combination, we present results achieved for the MUUFL Gulfport Hyperspectral and LiDAR Airborne Data Set. © Authors 2019.

关键词： Classification (of information)

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An authorization model for collaborative access control

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Journal of Zhejiang University-science C(computers and Electronics) 2010年第9期11卷 699-717页

作者： Chen-hua MA Guo-dong LU Jiong QIU Engineering and Computer Graphics Institute Zhejiang University Hangzhou 310027 China Department of Computer Science and Technology Hangzhou Dianzi University Hangzhou 310018 China

Collaborative access control is receiving growing attention in both military and commercial areas due to an urgent need to protect confidential resources and sensitive *** access control means that multiple subjects should participate to make access control decisions to prevent fraud or the abuse of *** approaches to access control cannot satisfy the requirements of collaborative access *** address this concern,we propose an authorization model for collaborative access *** central notions of the model are collaborative permission,collaboration constraint,and collaborative authorization policy,which make it possible to define the collaboration among multiple subjects involved in gaining a *** implementation architecture of the model is also ***,we present effective conflict detection and resolution methods for maintaining the consistency of collaborative authorization policies.

关键词： Collaborative access control Collaborative permission Conflict detection and resolution

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GPNST: An Improved Graphical Password Authentication Scheme Leveraging Neural Style Transfer Technique on Smartphones

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International Journal of Information Security 2025年第3期24卷 1-34页

作者： Ray, Palash Giri, Debasis Obaidat, Mohammad S. Jana, Manasi Sasmal, Mahuya Alenazi, Mohammed J. F. Haldia Institute of Technology Haldia India Maulana Abul Kalam Azad University of Technology Nadia India King Abdullah II School of Information Technology The University of Jordan Amman Jordan School of Computer and Communication Engineering University of Science and Technology Beijing Beijing China Department of Computational Intelligence School of Computing SRM University Kattankulathur India King Saud University Riyadh Saudi Arabia

The growing prevalence of smartphones and the increasing dependence on digital services have made it crucial to have authentication techniques that are both secure and user-friendly. This study examines the effectiveness and usability of graphical passwords named GPNST as an alternative authentication method on mobile devices. Graphical passwords use users’ capacity to remember visuals or patterns, offering a possible equilibrium between security and user pleasure. GPNST is a two-factor authentication technique that requires users to remember content and style images, or stylized images, as portfolio images. Additionally, a unique key token is assigned to each user device and securely sent to the server using the reversible data hiding approach, therefore mitigating several potential attacks. The research uses a combination of quantitative analysis to evaluate the strength of passwords and qualitative evaluations to measure user satisfaction and memorability. We investigate the influence of several design elements in graphical passwords, such as the intricacy of images and the layout of grids, on both the level of security and ease of use. In addition, the study evaluates the robustness of graphical passwords against popular forms of attacks, such as shoulder surfing and brute-force efforts. The findings provide valuable insights regarding the practicality of incorporating graphical passwords into smartphone authentication systems. This has implications for designers, developers, and users who are looking for secure and user-friendly solutions in the constantly changing field of mobile technology. The GPNST scheme demonstrates outstanding performance in our assessment test, with an accuracy rate of up to 94.80% and a login time of 9.61 seconds.

关键词： Static random access storage

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