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Solid model edit distance: a multi-application and multi-level schema for CAD model retrieval

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computer Aided Drafting,Design and Manufacturing 2017年第1期27卷 22-38页

作者： Wang Bin Hu Kaimo Li Dong Zhang Hui School of Software Tsinghua University Tsinghua National Laboratory for Information Science and Technology Department of Computer Graphics Technology Purdue University

We present the solid model edit distance(SMED),a powerful and flexible paradigm for exploiting shape similarities amongst CAD *** is designed to measure the magnitude of distortions between two CAD models in boundary representation(B-rep).We give the formal definition by analogy with graph edit distance,one of the most popular graph matching *** avoid the expensive computational cost potentially caused by exact computation,an approximate procedure based on the alignment of local structure sets is provided in *** order to verify the flexibility,we make intensive investigations on three typical applications in manufacturing industry,and describe how our method can be adapted to meet the various ***,a multilevel method is proposed to make further improvements of the presented algorithm on both effectiveness and efficiency,in which the models are hierarchically segmented into the configurations of *** results show that SMED serves as a reasonable measurement of shape similarity for CAD models,and the proposed approach provides remarkable performance on a real-world CAD model database.

关键词： CAD model retrieval solid model edit distance graph edit distance boundary representation

Proceduralization of urban models

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Proceduralization of urban models

IEEE Signal Processing and Communications Applications (SIU)

作者： İlke Demir Daniel G. Aliaga Bedrich Benes Computer Science Department Purdue University West Lafayette IN USA Computer Graphics Technology Purdue University West Lafayette IN USA

ISBN: (纸本)9781509064953

Architectural models have always played an important role in computer graphics, virtual environments, and urban planning; due to the size, detail and complexity of such models. Creating detailed and realistic buildings needs time and extensive coding as well as significant domain expertise. Observing the content creation problem and the challenges of procedural modeling, we identified and developed a generalized proceduralization framework, that converts existing 3D urban models into an easy to manipulate procedural form. Our proceduralization framework for urban spaces allows re-use of existing models in various formats by first conducting shape processing methods to find and exploit the repetitions and similarities to reveal the hidden high-level structural information, and then by using grammar discovery methods on those components to extract a representative grammar of the model. Additionally, we have proposed applications of such procedural representations, including completion of point cloud models and structure-aware synthesis tools for procedural editing.

关键词： Buildings Grammar Three-dimensional displays Urban areas Solid modeling Computational modeling Shape

How many matchings cover the nodes of a graph?

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arXiv 2018年

作者： Ferhat, Dehia Ait Király, Zoltán Sebo, András Stauffer, Gautier Mentor Graphics Montbonnot Saint Martin France Eötvös University Department of Computer Science Budapest Hungary CNRS G-SCOP Univ. Grenoble Alpes France Center of Excellence in Supply Chain Innovation and Transportation Kedge Business School Talence France

Given an undirected graph, are there k matchings whose union covers all of its nodes, that is, a matching-k-cover? A first, easy polynomial solution from matroid union is possible, as already observed by Wang, Song and Yuan (Mathematical Programming, 2014). However, it was not satisfactory neither from the algorithmic viewpoint nor for proving graphic theorems, since the corresponding matroid ignores the edges of the graph. We prove here, simply and algorithmically: all nodes of a graph can be covered with k ≥ 2 matchings if and only if for every stable set S we have |S| ≤ k · |N(S)|. When k = 1, an exception occurs: this condition is not enough to guarantee the existence of a matching-1-cover, that is, the existence of a perfect matching, in this case Tutte’s famous matching theorem (J. London Math. Soc., 1947) provides the right ‘good’ characterization. The condition above then guarantees only that a perfect 2-matching exists, as known from another theorem of Tutte (Proc. Amer. Math. Soc., 1953). Some results are then deduced as consequences with surprisingly simple proofs, using only the level of difficulty of bipartite matchings. We give some generalizations, as well as a solution for minimization if the edge-weights are non-negative, while the edge-cardinality maximization of matching-2-covers turns out to be already NP-hard. We have arrived at this problem as the line graph special case of a model arising for manufacturing integrated circuits with the technology called ‘Directed Self Assembly’. Copyright © 2018, The Authors. All rights reserved.

关键词： Undirected graphs

Continuous global optimization in surface reconstruction from an oriented point cloud

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arXiv 2017年

作者： Pan, Rongjiang Skala, Vaclav School of Computer Science and Technology Shandong University Jinan China Centre of Computer Graphics and Data Visualization Department of Computer Science and Engineering University of West Bohemia Plzen Czech Republic

We introduce a continuous global optimization method to the field of surface reconstruction from discrete noisy cloud of points with weak information on orientation. The proposed method uses an energy functional combining flux-based data-fit measures and a regularization term. A continuous convex relaxation scheme assures the global minima of the geometric surface functional. The reconstructed surface is implicitly represented by the binary segmentation of vertices of a 3D uniform grid and a triangulated surface can be obtained by extracting an appropriate isosurface. Unlike the discrete graph-cut solution, the continuous global optimization entails advantages like memory requirements, reduction of metrication errors for geometric quantities, allowing globally optimal surface reconstruction at higher grid resolutions. We demonstrate the performance of the proposed method on several oriented point clouds captured by laser scanners. Experimental results confirm that our approach is robust to noise, large holes and non-uniform sampling density under the condition of very coarse orientation information. Copyright © 2017, The Authors. All rights reserved.

关键词： Global optimization

A method for automatic forensic facial reconstruction based on dense statistics of soft tissue thickness

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arXiv 2018年

作者： Gietzen, Thomas Brylka, Robert Achenbach, Jascha Hebel, Katjazum Schömer, Elmar Botsch, Mario Schwanecke, Ulrich Schulze, Ralf RheinMain University of Applied Sciences Computing for New Media Wiesbaden Germany Bielefeld University Computer Graphics Group Bielefeld Germany University Medical Center of the Johannes Gutenberg University Mainz Department of Prosthetic Dentistry Mainz Germany Johannes Gutenberg University Mainz Institute of Computer Science Mainz Germany University Medical Center Johannes Gutenberg University Mainz Section of Oral Radiology Mainz Germany

In this paper, we present a method for automated estimation of a human face given a skull remain. The proposed method is based on three statistical models. A volumetric (tetrahedral) skull model encoding the variations of different skulls, a surface head model encoding the head variations, and a dense statistic of facial soft tissue thickness (FSTT). All data are automatically derived from computed tomography (CT) head scans and optical face scans. In order to obtain a proper dense FSTT statistic, we register a skull model to each skull extracted from a CT scan and determine the FSTT value for each vertex of the skull model towards the associated extracted skin surface. The FSTT values at predefined landmarks from our statistic are well in agreement with data from the literature. To recover a face from a skull remain, we first fit our skull model to the given skull. Next, we generate spheres with radius of the respective FSTT value obtained from our statistic at each vertex of the registered skull. Finally, we fit a head model to the union of all spheres. The proposed automated method enables a probabilistic face-estimation that facilitates forensic recovery even from incomplete skull remains. The FSTT statistic allows the generation of plausible head variants, which can be adjusted intuitively using principal component analysis. We validate our face recovery process using an anonymized head CT scan. The estimation generated from the given skull visually compares well with the skin surface extracted from the CT scan itself. Copyright © 2018, The Authors. All rights reserved.

关键词： Statistics

Intelligent system for cultural objects identification, damage assessment and restoration

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Intelligent system for cultural objects identification, dama...

作者： Sakkopoulos, Evangelos Pikoulis, Erion-Vasilis Viennas, Emmanouil Nodarakis, Nikolaos Cheilakou, Eleni Saint, Amani-Christiana Koui, Maria Tsakalidis, Athanasios Graphics Multimedia and GIS System Lab Computer Engineering and Informatics Department University of Patras Rio-PatrasGR-26504 Greece Department of Materials Science and Engineering NDT Lab School of Chemical Engineering National Technical University of Athens Greece

Cultural objects and art works need ongoing conservation interventions in order to be available for the next generations. The most object-friendly analysis approaches are based on non-destructive techniques (NDTs) that allow both the materials characterisation as well as the decay detection of cultural artefacts. Non-destructive testing and evaluation includes the employment of several methods such as the well-established technique of diffuse reflectance spectroscopy with fibre optics (FORS). Such techniques produce output with multiple series of data for multiple different pigment used in objects. In this work, we present a data management solution that contributes with: 1) a library of known reference pigments/colours;2) a proposed pattern matching technique that allows the automatic classification of any new pigment. The experimental evaluation results show that the data processing proposed is effective. Feedback is particularly encouraging as it allows automation and therefore radically decreased time for pigment/colour matching and identification. © 2017 Inderscience Enterprises Ltd.

关键词： Reflection

Convolutional Neural Networks for Epileptic Seizure Prediction

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arXiv 2018年

作者： Eberlein, Matthias Hildebrand, Raphael Tetzlaff, Ronald Hoffmann, Nico Kuhlmann, Levin Brinkmann, Benjamin Müller, Jens Technische Universität Dresden Faculty of Electrical and Computer Engineering Institute of Circuits and Systems Dresden01062 Germany Technische Universität Dresden Faculty of Computer Science Computer Graphics and Visualisation Dresden01062 Germany Faculty of Information Technology Monash University VIC Clayton3800 Australia Department of Medicine St Vincent's Hospital Melbourne VIC Fitzroy3065 Australia Mayo Systems Electrophysiology Laboratory Departments of Neurology and Biomedical Engineering Mayo Clinic RochesterMN55905 United States

Epilepsy is the most common neurological disorder and an accurate forecast of seizures would help to overcome the patient's uncertainty and helplessness. In this contribution, we present and discuss a novel methodology for the classification of intracranial electroencephalography (iEEG) for seizure prediction. Contrary to previous approaches, we categorically refrain from an extraction of hand-crafted features and use a convolutional neural network (CNN) topology instead for both the determination of suitable signal characteristics and the binary classification of preictal and interictal segments. Three different models have been evaluated on public datasets with long-term recordings from four dogs and three patients. Overall, our findings demonstrate the general applicability. In this work we discuss the strengths and limitations of our methodology. Copyright © 2018, The Authors. All rights reserved.

关键词： Electroencephalography

Surface reconstruction with higher-order smoothness

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arXiv 2017年

作者： Pan, Rongjiang Skala, Vaclav School of Computer Science and Technology Shandong University Jinan250100 China Centre of Computer Graphics and Data Visualization Department of Computer Science and Engineering University of West Bohemia Plzen Czech Republic

This work proposes a method to reconstruct surfaces with higher-order smoothness from noisy 3D measurements. The reconstructed surface is implicitly represented by the zero level-set of a continuous valued embedding function. The key idea is to find a function whose higher-order derivatives are regularized and whose gradient is best aligned with a vector field defined by the input point set. In contrast to methods based on the first-order variation of the function that are biased towards the constant functions and treat the extraction of the isosurface without aliasing artifacts as an afterthought, we impose higher-order smoothness directly on the embedding function. After solving a convex optimization problem with a multi-scale iterative scheme, a triangulated surface can be extracted using the marching cubes algorithm. We demonstrated the proposed method on several data sets obtained from raw laser-scanners and multi-view stereo approaches. Experimental results confirm that our approach allows us to reconstruct smooth surfaces from points in the presence of noise, outliers, large missing parts and very coarse orientation information. Copyright © 2017, The Authors. All rights reserved.

关键词： Convex optimization

Identifying intracortical partial voluming effects using cortical surface normals in quantitative MRI T1 maps sensitive to microstructure

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Identifying intracortical partial voluming effects using cor...

Workshops on Image processing for the medicine, 2016

作者： Dinse, Juliane Schäfer, Andreas Bazin, Pierre-Louis Weiskopf, Nikolaus Max Planck Institute of Cognitive and Brain Science Leipzig Germany Simulation and Graphics Department Faculty of Computer Science Otto-von-Guericke University Magdeburg Germany Wellcome Trust Center for Neuroimaging Institute for Neurology University College London London United Kingdom

ISBN: (纸本)9783662494646

Partial voluming is a known problem in medical imaging. It occurs at high contrast edges between different structures. Image segmentation tasks can account for this type of effect to a certain degree, but residual intensity effects in structures located further away from affected edges remain. This paper focuses on partial volume (PV) effects at the interface between gray matter and cerebrospinal fluid in the brain when imaged using high-field magnetic resonance imaging (MRI). Here, we use cortical surface normals for spatially locating PV-induced effects on MRI measures of cortical microstructure. We demonstrate that especially in very narrow sulcal banks of the cortex, PV effects significantly influence cortical MRI intensities, but only up to a certain cortical depth. The method allows to investigate and better understand PV effects in the cortex to identify locations in which the MRI intensities can be fully trusted. The results may prove to be useful for future PV correction methods in brain segmentation. Also, cortical area studies may benefit from better PV estimation in order to yield more precise and confiding results on microstructure and areal extent. © Springer-Verlag Berlin Heidelberg 2016.

关键词： Magnetic resonance imaging