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Radiance-based color calibration for image-based modeling with multiple cameras

Science China(Information Sciences) 2012年第7期55卷 1509-1519页

作者： ZHAO Xu 1,2 ,ZHOU Zhong 1,2 & WU Wei 1,2 1 State Key Laboratory of Virtual Reality Technology and Systems,Beihang University,Beijing 100191,China 2 School of Computer Science and Engineering,Beihang University,Beijing 100191,China 1. State Key Laboratory of Virtual Reality Technology and Systems Beihang University Beijing 100191 China2. School of Computer Science and Engineering Beihang University Beijing 100191 China

Photo-consistency estimation is an important part for many image-based modeling *** paper presents a novel radiance-based color calibration method to reduce the uncertainty of photo-consistency estimation across multiple *** idea behind our method is to convert colors into a uniform radiometric color space in which multiple image data are *** results demonstrate that our method can achieve comparable color calibration effect without adjusting camera parameters and is more robust than other existing ***,we obtain an auto-determined threshold for photo-consistency check,which will lead to a better performance than existing photo-consistency based reconstruction algorithms.

关键词： color calibration photo-consistency estimation multi-camera system image-based modeling

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Brushwork master: Chinese ink painting synthesis for animating brushwork process

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COMPUTER ANIMATION AND VIRTUAL WORLDS 2020年第4-5期31卷 e1949-e1949页

作者： Yang, Lijie Xu, Tianchen Du, Jixiang Zhang, Hongbo Wu, Enhua Huaqiao Univ Coll Comp Sci & Technol 668 Jimei Ave Xiamen Fujian Peoples R China Chinese Acad Sci Inst Software State Key Lab Comp Sci Beijing Peoples R China Univ CAS Beijing Peoples R China Univ Macau Fac Sci & Technol FST Macau Peoples R China

Generally, it is regarded as challenge work to grasp the drawing style of an ancient masterpiece in Chinese painting learning. This paper presents a novel approach to the generation of a Chinese ink painting in a certain style and animating its brushwork process with expert skills. In order to demonstrate the techniques of brush and ink inside a stroke, a serials of geometric properties of a brush stroke, are first extracted, then through rational deformation calculation, the best stroke source is mapped onto the stroking path, which is sketched by the user, and finally a new Chinese painting can be synthesized by style migration and natural stroke composition. So with the generated strokes, the lifelike brushwork process of the new painting can be represented dramatically. Actually, by showing the authentic painting process, the tool we implemented helps the learners, who have no profound skills and knowledge in domain of Chinese painting, master the essence of a great painting style, and also provides an easy way to art creation and the comprehension of mysterious Chinese traditional art.

关键词： 2D object synthesis Chinese ink painting computer animation drawing process image-based modeling

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Uncertainty Quantification for Non-invasive Assessment of Pressure Drop Across a Coarctation of the Aorta Using CFD

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CARDIOVASCULAR ENGINEERING AND TECHNOLOGY 2018年第4期9卷 582-596页

作者： Bruening, Jan Hellmeier, Florian Yevtushenko, Pavlo Kuehne, Titus Goubergrits, Leonid Charite Univ Med Berlin Inst Imaging Sci & Computat Modelling Cardiovasc Augustenburger Pl 1Forum 4-0-0561 D-13353 Berlin Germany German Heart Ctr Berlin Dept Congenital Heart Dis Unit Cardiovasc Imaging Berlin Germany DZHK German Ctr Cardiovasc Res Partner Site Berlin Berlin Germany

Purpose-Numerical assessment of the pressure drop across an aortic coarctation using CFD is a promising approach to replace invasive catheter-based measurements. The aim of this study was to investigate and quantify the uncertainty of numerical calculation of the pressure drop introduced during two essential steps of medical image processing: segmentation of the patient-specific geometry and measurement of patient-specific flow rates from 4D-flow-MRI. Methods-based on the baseline segmentation, geometries with different stenosis diameters were generated for a sample of ten patients. The pressure drop generated by these geometries was calculated for different volume flow rates using computational fluid dynamics. based on these simulations, a second order polynomial fit was calculated. based on these polynomial fits an uncertainty of pressure drop calculation was quantified. Results-The calculated pressure drop values varied strongly between the patients. In four patients, pressure drops above and below the clinical threshold of 20mmHg were found. The median standard deviation of the pressure drop was 2.3mmHg. The sensitivity of the pressure drop toward changes in the volume flow rate or the stenosis geometry varied between patients. Conclusion-The uncertainty of numerical pressure drop calculation introduced by uncertainties during image segmentation and measurement of volume flow rates was comparable to the uncertainty of pressure drop measurements using invasive catheterization. However, in some patients this uncertainty would have led to different treatment decision. Therefore, patient-specific uncertainty assessment might help to better understand the reliability of a numerically calculated biomarker as the pressure drop across an aortic coarctation.

关键词： Coarctation of the aorta Computational fluid dynamics image-based modeling Hemodynamics Uncertainty analysis Non-invasive diagnosis

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3D braid guide hair reconstruction using electroluminescent wires

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VISUAL COMPUTER 2018年第6-8期34卷 793-804页

作者： Hachmann, Hendrik Awiszus, Maren Rosenhahn, Bodo Leibniz Univ Hannover Inst Informat Verarbeitung Appelstr 9A D-30167 Hannover Germany

In this paper we propose a novel braid acquisition and 3D guide hair reconstruction method. Low-cost electroluminescent wires are woven into the braided hair strands which are thereby illuminated from the inside. Unlike state-of-the-art hair reconstruction approaches, we do not need image texture information, data-driven prior knowledge or manual editing. Instead, our workflow reconstructs braid guide hairs fully automatically using semi-open-end 3D active curves on images recorded from multiple views. The proposed pipeline extracts non-surface, internal 3D information which enables morphing and inter-character hairdo-transfer. In state-of-the-art methods, those abilities typically exist for virtually created hairstyles and not for reconstructed hairstyles. Furthermore, using the new acquisition scheme we provide a novel type of data set to the community.

关键词： Hair modeling image-based modeling 3D reconstruction Braids

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A model-based approach for estimation of changes in lumbar segmental kinematics associated with alterations in trunk muscle forces

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JOURNAL OF BIOMECHANICS 2018年 70卷 82-87页

作者： Shojaei, Iman Arjmand, Navid Meakin, Judith R. Bazrgari, Babak Univ Kentucky F Joseph Halcomb MD Dept Biomed Engn 3 514E Robot & Mfg Bldg Lexington KY 40506 USA Sharif Univ Technol Dept Mech Engn Tehran Iran Univ Exeter Sch Phys & Astron Phys BldgStocker Rd Exeter EX4 4QL Devon England

The kinematics information from imaging, if combined with optimization-based biomechanical models, may provide a unique platform for personalized assessment of trunk muscle forces (TMFs). Such a method, however, is feasible only if differences in lumbar spine kinematics due to differences in TMFs can be captured by the current imaging techniques. A finite element model of the spine within an optimization procedure was used to estimate segmental kinematics of lumbar spine associated with five different sets of TMFs. Each set of TMFs was associated with a hypothetical trunk neuromuscular strategy that optimized one aspect of lower back biomechanics. For each set of TMFs, the segmental kinematics of lumbar spine was estimated for a single static trunk flexed posture involving, respectively, 40 degrees and 10 degrees of thoracic and pelvic rotations. Minimum changes in the angular and translational deformations of a motion segment with alterations in TMFs ranged from 0 degrees to 0.7 degrees and 0 mm to 0.04 mm, respectively. Maximum changes in the angular and translational deformations of a motion segment with alterations in TMFs ranged from 2.4 degrees to 7.6 degrees and 0.11 mm to 0.39 mm, respectively. The differences in kinematics of lumbar segments between each combination of two sets of TMFs in 97% of cases for angular deformation and 55% of cases for translational deformation were within the reported accuracy of current imaging techniques. Therefore, it might be possible to use image-based kinematics of lumbar segments along with computational modeling for personalized assessment of TMFs. (C) 2017 Elsevier Ltd. All rights reserved.

关键词： Trunk muscle forces Finite element analysis Optimization procedures Trunk neuromuscular strategies Lumbar segmental kinematics image-based modeling

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3D characterization of porosity in an air plasma-sprayed thermal barrier coating and its effect on thermal conductivity

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JOURNAL OF THE AMERICAN CERAMIC SOCIETY 2018年第6期101卷 2482-2492页

作者： Zhang, Xun Kulczyk-Malecka, Justyna Carr, James Xiao, Ping Withers, Philip J. Univ Manchester Sch Mat Henry Moseley Xray Imaging Facil Manchester Lancs England Univ Manchester Sch Mat Manchester Lancs England Manchester Metropolitan Univ Surface Engn Grp Manchester Lancs England

Air plasma spray (APS) thermal barrier coatings (TBCs) contain pores, cracks and splat interfaces that are preferentially aligned normal to the heat flux direction. These significantly reduce (by as much as 50%) the thermal conductivity over a fully dense coating. Here the microstructures of APS thermal barrier coatings (TBCs) have been characterized in 3D using X-ray microcomputed tomography (-CT). Pores larger than 2.8m(3) are resolved and their contribution to thermal conductivity reduction is evaluated using image-based microstructurally realistic numerical models. However, the models overestimate (by almost 50%) the measured thermal conductivity of the as-deposited TBC sample. It is shown that this discrepancy is due to very fine (micrometer and submicrometer) cracks which readily sinter after short-term exposure to temperatures representative of TBC operating conditions causing the measured thermal conductivity to rise to within 15% of that predicted. This suggests that under the realistic service conditions, the 3D image-based models based on CT images provide a good indicator of the likely long-term TBC performance. Virtual experiments showed that for the retained pores, the larger pores which are flatter and more oriented in the plane of the APS splats, contribute disproportionately to the beneficial reduction in thermal conductivity. Our results demonstrate that X-ray imaging is a useful tool in establishing APS process conditions that give rise to a beneficial distribution of such pores.

关键词： high temperature image-based modeling turbine blade yttria-stabilized zirconia

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Micro-photogrammetric and morphometric differentiation of cut marks on bones using metal knives, quartzite, and flint flakes

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ARCHAEOLOGICAL AND ANTHROPOLOGICAL SCIENCES 2018年第4期10卷 805-816页

作者： Angel Mate-Gonzalez, Miguel Francisco Palomeque-Gonzalez, Juan Yravedra, Jose Gonzalez-Aguilera, Diego Dominguez-Rodrigo, Manuel Univ Complutense Madrid CAI Arqueometria & Anal Arqueol Prof Aranguren S-N Madrid 28040 Spain Univ Salamanca Polytech Sch Avila Dept Cartog & Terrain Engn Hornos Caleros 50 Avila 05003 Spain Univ Complutense Madrid Dept Prehist Prof Aranguren S-N Madrid 28040 Spain IDEA Inst Evolut Africa Museo Origenes Plaza San Andres 2 Madrid 28005 Spain

In a previous article, we presented an innovative method to analyze cut marks produced with metal tools on animal bones from a metrical and tridimensional perspective (Mat,-Gonzalez et al. 2015). Such analysis developed a low-cost alternative technique to traditional microscopic methods for the tridimensional reconstruction of marks, using their measurements and sections. This article presents the results of an experimental study to test this photogrammetric and morphometric method for differentiating cut marks generated with metal, flint, and quartzite flakes. The results indicate statistically significant differences among cut marks produced by these three types of raw material. These results encourage the application of this method to archeological assemblages in order to establish a link between carcass processing and lithic reduction sequences on different raw materials and also to define the kind of tools used during butchery.

关键词： Taphonomy Cut marks Micro-photogrammetry Computer vision image-based modeling Rawmaterial

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Reduced Order Models for Transstenotic Pressure Drop in the Coronary Arteries

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JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME 2019年第3期141卷 031005-031005页

作者： Mirramezani, Mehran Diamond, Scott L. Litt, Harold I. Shadden, Shawn C. Univ Calif Berkeley Dept Mech Engn Berkeley CA 94720 USA Univ Calif Berkeley Dept Math Berkeley CA 94720 USA Univ Penn Inst Med & Engn Dept Chem & Biomol Engn Philadelphia PA 19104 USA Univ Penn Perelman Sch Med Dept Radiol Philadelphia PA 19104 USA

The efficacy of reduced order modeling for transstenotic pressure drop in the coronary arteries is presented. Coronary artery disease is a leading cause of death worldwide and the computation of pressure drop in the coronary arteries has become a standard for evaluating the functional significance of a coronary stenosis. Comprehensive models typically employ three-dimensional (3D) computational fluid dynamics (CFD) to simulate coronary blood flow in order to compute transstenotic pressure drop at the arterial stenosis. In this study, we evaluate the capability of different hydrodynamic models to compute transstenotic pressure drop. Models range from algebraic formulae to one-dimensional (1D), two-dimensional (2D), and 3D time-dependent CFD simulations. Although several algebraic pressure-drop formulae have been proposed in the literature, these models were found to exhibit wide variation in predictions. Nonetheless, we demonstrate an algebraic formula that provides consistent predictions with 3D CFD results for various changes in stenosis severity, morphology, location, and flow rate. The accounting of viscous dissipation and flow separation were found to be significant contributions to accurate reduce order modeling of transstenotic coronary hemodynamics.

关键词： coronary artery stenosis fractional flow reserve hemodynamics image-based modeling noninvasive pressure drop

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Procedure-based component and architecture modeling from a single image

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VISUAL COMPUTER 2016年第2期32卷 151-166页

作者： Hou, Fei Qin, Hong Qi, Yue Beihang Univ State Key Lab Virtual Real Technol & Syst Beijing 100191 Peoples R China Nanyang Technol Univ Sch Comp Engn Singapore 639798 Singapore SUNY Stony Brook NYU Dept Comp Sci New York NY USA

This paper advocates a new component-aware framework to reconstruct 3D architecture from a single image. Different from existing work, our motivation is to obtain a complete set of semantically correct 3D architectural components, which enables part reusability towards rapid model reproduction and facilitates model variation. The core of our system is a novel algorithm to adaptively segment repeated curved stripes (e. g., roof tiles, building floors) into individual elements, based on which 3D dimensions as well as architectural components are derived from a single image. Specially for Chinese architectures, we further devise an interactive method to identify outer columns based on userspecified inner columns. Finally, 3D components are generated and shape rules are derived, from which the buildings and their variants are constructed. Our newcomponent-aware framework minimizes the use of data resource (i. e., one single image) and emphasizes component utility during rapid 3D architecture reproduction by advocating a component-aware approach.

关键词： Architectural modeling image-based modeling Procedural modeling

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Intra-site Digital Documentation of the Ancient Maya city of Palenque, Mexico 3

Intra-site Digital Documentation of the Ancient Maya city of...

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3rd Digital Heritage International Congress (DigitalHERITAGE) / 24th International Conference on Virtual Systems and Multimedia (VSMM)

作者： Lercari, Nicola Campiani, Arianna Stuardo, Rodrigo Liendo Univ Calif Merced Dept Anthropol & Heritage Studies Merced CA 95343 USA Univ Nacl Autonoma Mexico Anthropol Res Inst Mexico City DF Mexico

ISBN: (纸本)9781728102924

Since archaeological and historical sites occur in relatively restricted areas, they are non-renewable resources, and like natural resources, are sensitive to human and natural intervention and should be cared for, curated, and preserved for local, national, and international communities. Unfortunately, over the last two decades, climate change, growing political instability, and looting have led to the deterioration of numerous Mesoamerican archaeological sites. In this scenario, digital documentation and remote sensing technologies become invaluable resources to record, monitor, and preserve the diverse Maya cultural heritage of the Southern Mexican state of Chiapas. Current efforts in digitizing and mapping archaeological sites in Mesoamerica mostly use an inter- site approach that leverages airborne Light Detection and Ranging (LiDAR). Nonetheless, the high cost of commercial LiDAR and its current limits in capturing excavated vertical structures urged us to explore alternative approaches to digital documentation able to inform site monitoring and physical conservation and to develop multimodal 3-D survey workflows that can be adopted throughout Mesoamerica. This paper thus presents the preliminary results of our intra-site digital documentation work at the World Heritage site of Palenque, Mexico. It also discusses the potential of integrating intra-site and inter-site digital documentation technologies, such as Unmanned Aerial Systems, image-based modeling, terrestrial laser scanning, and drone-based airborne LiDAR with ground truthing and physical conservation interventions to foster built heritage interpretation, conservation, and preservation in Mexico and in other countries with a high concentration of heritage sites but limited research funding.

关键词： Maya archaeology digital documentation intra-site inter-site image-based modeling unmanned aerial systems 3-D scanning digital preservation conservation

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