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Template Assembly for Detailed Urban Reconstruction

COMPUTER GRAPHICS FORUM 2015年第2期34卷 217-228页

作者： Nan, Liangliang Jiang, Caigui Ghanem, Bernard Wonka, Peter KAUST Thuwal Saudi Arabia

We propose a new framework to reconstruct building details by automatically assembling 3D templates on coarse textured building models. In a preprocessing step, we generate an initial coarse model to approximate a point cloud computed using Structure from Motion and Multi View Stereo, and we model a set of 3D templates of facade details. Next, we optimize the initial coarse model to enforce consistency between geometry and appearance (texture images). Then, building details are reconstructed by assembling templates on the textured faces of the coarse model. The 3D templates are automatically chosen and located by our optimization-based template assembly algorithm that balances image matching and structural regularity. In the results, we demonstrate how our framework can enrich the details of coarse models using various data sets.

关键词： Categories and Subject Descriptors (according to ACM CCS) I.3.5 [Computer Graphics]: Computational Geometry and Object Modeling&mdash geometric algorithms languages and systems

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Accurate GPU-accelerated surface integrals for moment computation

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COMPUTER-AIDED DESIGN 2011年第10期43卷 1284-1295页

作者： Krishnamurthy, Adarsh McMains, Sara Univ Calif Berkeley Comp Aided Design & Mfg Lab Berkeley CA 94720 USA

We present algorithms for computing accurate moments of solid models that are represented using multiple trimmed NURBS surfaces and triangles. Our algorithms make use of programmable Graphics Processing Units (GPUs) to accelerate the moment computations. For NURBS surfaces, we evaluate the surface coordinates and normals accurately, with theoretical bounds, using our CPU NURBS evaluator. We have developed a framework that makes use of this data to evaluate surface integrals of trimmed NURBS surfaces in real time. Since typical solid models also contain flat planes that are usually tessellated into triangles, our framework also includes CPU acceleration of the moment contributions of such flat faces. Using our framework, we can compute volume and moments of solid models with theoretical guarantees. Our algorithms support local geometry changes, which is useful for providing interactive feedback to the designer while the solid model is being designed. We can compute the center of mass and check for stability of the solid model interactively. Other applications of such real-time moment computation include deformation modeling, animation, and physically based simulations. (C) 2011 Elsevier Ltd. All rights reserved.

关键词： geometric algorithms Moments Volume NURBS GPU Hybrid CPU/GPU algorithms

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Partial Bi-Invariance of SE(3) Metrics

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JOURNAL OF COMPUTING AND INFORMATION SCIENCE IN ENGINEERING 2015年第1期15卷 011008页

作者： Chirikjian, Gregory S. Johns Hopkins Univ Dept Mech Engn Robot & Prot Kinemat Lab Baltimore MD 21218 USA

In a flurry of articles in the mid to late 1990s, various metrics for the group of rigid-body motions, SE(3), were introduced for measuring distance between any two reference frames or rigid-body motions. During this time, it was shown that one can choose a smooth distance function that is invariant under either all left shifts or all right shifts, but not both. For example, if one defines the distance between two reference frames to be an appropriately weighted Frobenius norm of the difference of the corresponding homogeneous transformation matrices, this will be invariant under left shifts by arbitrary rigid-body motions. However, this is not the full picture-other invariance properties exist. Though the Frobenius norm is not invariant under right shifts by arbitrary rigid-body motions, for an appropriate weighting it is invariant under right shifts by pure rotations. This is also true for metrics based on the Lie-theoretic logarithm. This paper goes further to investigate the full invariance properties of distance functions on SE(3), clarifying the full subsets of motions under which both left and right invariance is possible.

关键词： Rotation Screws geometric algorithms algorithms Degrees of freedom

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Discovery of Intrinsic Primitives on Triangle Meshes

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COMPUTER GRAPHICS FORUM 2011年第2期30卷 365-374页

作者： Solomon, Justin Ben-Chen, Mirela Butscher, Adrian Guibas, Leonidas Stanford Univ Stanford CA 94305 USA

The discovery of meaningful parts of a shape is required for many geometry processing applications, such as parameterization, shape correspondence, and animation. It is natural to consider primitives such as spheres, cylinders and cones as the building blocks of shapes, and thus to discover parts by fitting such primitives to a given surface. This approach, however, will break down if primitive parts have undergone almost-isometric deformations, as is the case, for example, for articulated human models. We suggest that parts can be discovered instead by finding intrinsic primitives, which we define as parts that posses an approximate intrinsic symmetry. We employ the recently-developed method of computing discrete approximate Killing vector fields (AKVFs) to discover intrinsic primitives by investigating the relationship between the AKVFs of a composite object and the AKVFs of its parts. We show how to leverage this relationship with a standard clustering method to extract k intrinsic primitives and remaining asymmetric parts of a shape for a given k. We demonstrate the value of this approach for identifying the prominent symmetry generators of the parts of a given shape. Additionally, we show how our method can be modified slightly to segment an entire surface without marking asymmetric connecting regions and compare this approach to state-of-the-art methods using the Princeton Segmentation Benchmark.

关键词： Computer Graphics [I.3.5]: Computational Geometry and Object Modeling geometric algorithms languages and systems

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Bilateral recovering of sharp edges on feature-insensitive sampled meshes

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IEEE TRANSACTIONS ON VISUALIZATION AND COMPUTER GRAPHICS 2006年第4期12卷 629-639页

作者： Wang, CCL Chinese Univ Hong Kong Dept Automat & Comp Aided Engn Shatin Hong Kong Peoples R China

A variety of computer graphics applications sample surfaces of 3D shapes in a regular grid without making the sampling rate adaptive to the surface curvature or sharp features. Triangular meshes that interpolate or approximate these samples usually exhibit relatively big error around the insensitive sampled sharp features. This paper presents a robust general approach conducting bilateral filters to recover sharp edges on such insensitive sampled triangular meshes. Motivated by the impressive results of bilateral filtering for mesh smoothing and denoising, we adopt it to govern the sharpening of triangular meshes. After recognizing the regions that embed sharp features, we recover the sharpness geometry through bilateral filtering, followed by iteratively modifying the given mesh's connectivity to form singlewide sharp edges that can be easily detected by their dihedral angles. We show that the proposed method can robustly reconstruct sharp edges on feature-insensitive sampled meshes.

关键词： boundary representations geometric algorithms languages systems

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Identifying rectangles in laser range data for urban scene reconstruction

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COMPUTERS & GRAPHICS-UK 2011年第3期35卷 719-725页

作者： van Lankveld, Thijs van Kreveld, Marc Veltkamp, Remco Univ Utrecht Dept Informat & Comp Sci NL-3584 CC Utrecht Netherlands

In urban scenes, many of the surfaces are planar and bounded by simple shapes. In a laser scan of such a scene, these simple shapes can still be identified. We present a one-parameter algorithm that can identify point sets on a plane for which a rectangle is a fitting boundary. These rectangles have a guaranteed density: no large part of the rectangle is empty of points. We prove that our algorithm identifies all angles for which a rectangle fits the point set of size n in O(nlogn) time. We evaluate our method experimentally on 13 urban data sets and we compare the rectangles found by our algorithm to the a-shape as a surface boundary. (C) 2011 Elsevier Ltd. All rights reserved.

关键词： Boundary representations Computational geometry Object modeling geometric algorithms

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Guided Mesh Normal Filtering

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COMPUTER GRAPHICS FORUM 2015年第7期34卷 23-34页

作者： Zhang, Wangyu Deng, Bailin Zhang, Juyong Bouaziz, Sofien Liu, Ligang Univ Sci & Technol China Hefei Anhui Peoples R China Ecole Polytech Fed Lausanne CH-1015 Lausanne Switzerland Univ Hull Kingston Upon Hull HU6 7RX N Humberside England

The joint bilateral filter is a variant of the standard bilateral filter, where the range kernel is evaluated using a guidance signal instead of the original signal. It has been successfully applied to various image processing problems, where it provides more flexibility than the standard bilateral filter to achieve high quality results. On the other hand, its success is heavily dependent on the guidance signal, which should ideally provide a robust estimation about the features of the output signal. Such a guidance signal is not always easy to construct. In this paper, we propose a novel mesh normal filtering framework based on the joint bilateral filter, with applications in mesh denoising. Our framework is designed as a two-stage process: first, we apply joint bilateral filtering to the face normals, using a properly constructed normal field as the guidance;afterwards, the vertex positions are updated according to the filtered face normals. We compute the guidance normal on a face using a neighboring patch with the most consistent normal orientations, which provides a reliable estimation of the true normal even with a high-level of noise. The effectiveness of our approach is validated by extensive experimental results.

关键词： Categories and Subject Descriptors (according to ACM CCS) I.3.5 [Computer Graphics]: Computational Geometry and Object Modeling&mdash geometric algorithms languages and systems

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Meshless Harmonic Volumetric Mapping Using Fundamental Solution Methods

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IEEE TRANSACTIONS ON AUTOMATION SCIENCE AND ENGINEERING 2009年第3期6卷 409-422页

作者： Li, Xin Guo, Xiaohu Wang, Hongyu He, Ying Gu, Xianfeng Qin, Hong Louisiana State Univ Dept Elect & Comp Engn Baton Rouge LA 70803 USA Louisiana State Univ Ctr Computat & Technol Baton Rouge LA 70803 USA SUNY Stony Brook Dept Comp Sci Stony Brook NY 11794 USA Univ Texas Dallas Dept Comp Sci Richardson TX 75083 USA Nanyang Technol Univ Sch Comp Engn Singapore 639798 Singapore

Harmonic volumetric mapping aims to establish a smooth bijective correspondence between two solid shapes with the same topology. In this paper, we develop an automatic meshless method for creating such a mapping between two given objects. With the shell surface mapping as the boundary condition, we first solve a linear system constructed by a boundary method called the method of fundamental solution, and then represent the mapping using a set of points with different weights in the vicinity of the shell of the given model. Our algorithm is a true meshless method (without the need of any specific meshing structure within the solid interior) and the behavior of the interior region is directly determined by the boundary, which can improve the computational efficiency and robustness significantly. Therefore, our algorithm can be applied to massive volume data sets with various geometric primitives and topological types. We demonstrate the utility and efficacy of our algorithm in information transfer, shape registration, deformation sequence analysis, tetrahedral remeshing, and solid texture synthesis. Note to Practitioners-Building a one-to-one smooth correspondence between two solid geometric models is a fundamental problem. It directly applies to shape registration: when we have two solid shapes matched, we can easily compute and visualize for analysis purpose where and how much do they differ. Another important application is generating regular connectivity for arbitrary solid objects. This is performed by transferring regular structure from a canonical object to our target object once the correspondence (mapping) is created. Given two solid models, we can automatically compute a physically natural mapping between them. This "physically natural" property is characterized by so called harmonicity, which measures the smoothness of the mapping function, and is represented by the harmonic energy. A map with minimized harmonic energy means it is smoothest and natural;and

关键词： Computational geometry and object modeling computer graphics computing methodologies geometric algorithms

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Advanced Polyphonic Music Pattern Matching algorithms with Timing Invariances 9th

Advanced Polyphonic Music Pattern Matching Algorithms with T...

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9th International Conference on Mathematics and Computation in Music (MCM)

作者： Laaksonen, Antti Lemstrom, Kjell Univ Helsinki Dept Comp Sci Helsinki Finland

ISBN: (纸本)9783031606373;9783031606380

This paper considers polyphonic pattern matching in symbolically encoded music under transposition invariance. We show how, in two specific retrieval problems, the worst-case time complexities can be improved by an order of magnitude by applying a relatively straight-forward algorithm design technique. Moreover, the technique applies to most of the previously best-known algorithms for the other cases of the problem category, giving comparable worst-case running times. In general, given two point sets, a musical work T and a pattern P, the task is to find possibly transposed occurrences of P in T. The occurrences may be full or partial, with or without time-warping or time-scaling. The technique uses a merge-like approach to incrementally build pattern occurrences using sorted lists of notes. The algorithms search for incomplete matches that are subsequently extended as far as possible.

关键词： Music pattern matching geometric algorithms timing invariances

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Learning 3D Deformation of Animals from 2D Images

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COMPUTER GRAPHICS FORUM 2016年第2期35卷 365-374页

作者： Kanazawa, Angjoo Kovalsky, Shahar Basri, Ronen Jacobs, David Univ Maryland Coll Pk College Pk MD 20742 USA Weizmann Inst Sci IL-76100 Rehovot Israel

Understanding how an animal can deform and articulate is essential for a realistic modification of its 3D model. In this paper, we show that such information can be learned from user-clicked 2D images and a template 3D model of the target animal. We present a volumetric deformation framework that produces a set of new 3D models by deforming a template 3D model according to a set of user-clicked images. Our framework is based on a novel locally-bounded deformation energy, where every local region has its own stiffness value that bounds how much distortion is allowed at that location. We jointly learn the local stiffness bounds as we deform the template 3D mesh to match each user-clicked image. We show that this seemingly complex task can be solved as a sequence of convex optimization problems. We demonstrate the effectiveness of our approach on cats and horses, which are highly deformable and articulated animals. Our framework produces new 3D models of animals that are significantly more plausible than methods without learned stiffness.

关键词： Categories and Subject Descriptors (according to ACM CCS) I.3.5 [Computer Graphics]: Computational Geometry and Object Modeling&mdash geometric algorithms languages and systems

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