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SAFE: Structure-aware facade editing

COMPUTER GRAPHICS FORUM 2014年第2期33卷 83-93页

作者： Minh Dang Ceylan, Duygu Neubert, Boris Pauly, Mark Ecole Polytech Fed Lausanne CH-1015 Lausanne Switzerland

Many man-made objects, in particular building facades, exhibit dominant structural relations such as symmetry and regularity. When editing these shapes, a common objective is to preserve these relations. However, often there are numerous plausible editing results that all preserve the desired structural relations of the input, creating ambiguity. We propose an interactive facade editing framework that explores this structural ambiguity. We first analyze the input in a semi-automatic manner to detect different groupings of the facade elements and the relations among them. We then provide an incremental editing process where a set of variations that preserve the detected relations in a particular grouping are generated at each step. Starting from one input example, our system can quickly generate various facade configurations.

关键词： Categories and Subject Descriptors (according to ACM CCS) I.3.5 [Computer Graphics] Computer Graphics&mdash computational geometry and object modeling

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Interactive Mesh Cutting Using Constrained Random Walks

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IEEE TRANSACTIONS ON VISUALIZATION AND COMPUTER GRAPHICS 2011年第3期17卷 357-367页

作者： Zhang, Juyong Zheng, Jianmin Cai, Jianfei Nanyang Technol Univ Sch Comp Engn Singapore 639798 Singapore

This paper considers the problem of interactively finding the cutting contour to extract components from an existing mesh. First, we propose a constrained random walks algorithm that can add constraints to the random walks procedure and thus allows for a variety of intuitive user inputs. Second, we design an optimization process that uses the shortest graph path to derive a nice cut contour. Then a new mesh cutting algorithm is developed based on the constrained random walks plus the optimization process. Within the same computational framework, the new algorithm provides a novel user interface for interactive mesh cutting that supports three typical user inputs and also their combinations: 1) foreground/background seed inputs: the user draws strokes specifying seeds for "foreground" (i.e., the part to be cut out) and "background" (i.e., the rest);2) soft constraint inputs: the user draws strokes on the mesh indicating the region which the cuts should be made nearby;and 3) hard constraint inputs: the marks which the cutting contour must pass. The algorithm uses feature sensitive metrics that are based on surface geometric properties and cognitive theory. The integration of the constrained random walks algorithm, the optimization process, the feature sensitive metrics, and the varieties of user inputs makes the algorithm intuitive, flexible, and effective as well. The experimental examples show that the proposed cutting method is fast, reliable, and capable of producing good results reflecting user intention and geometric attributes.

关键词： computational geometry and object modeling interaction techniques geometric algorithms

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A web system of virtual morphometric globes for Mars and the Moon

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PLANETARY AND SPACE SCIENCE 2018年第Sep.期159卷 105-109页

作者： Florinsky, I., V Garov, A. S. Karachevtseva, I. P. Russian Acad Sci Keldysh Inst Appl Math Inst Math Problems Biol Pushchino 142290 Moscow Region Russia Moscow State Univ Geodesy & Cartog MIIGAiK Extraterr Lab 4 Gorokhovsky Lane Moscow 105064 Russia

We developed a web system of virtual morphometric globes for Mars and the Moon. As the initial data, we used 15-arc-minutes gridded global digital elevation models (DEMs) extracted from the Mars Orbiter Laser Altimeter (MOLA) and the Lunar Orbiter Laser Altimeter (LOLA) gridded archives. We derived global digital models of sixteen morphometric variables including horizontal, vertical, minimal, and maximal curvatures, as well as catchment area and topographic index. The morphometric models were integrated into the web system developed as a distributed application consisting of a client front-end and a server back-end. The following main functions are implemented in the system: (1) selection of a morphometric variable;(2) two-dimensional visualization of a calculated global morphometric model;(3) 3D visualization of a calculated global morphometric model on the sphere surface;(4) change of a globe scale;and (5) globe rotation by an arbitrary angle. Free, real-time web access to the system is provided. The web system of virtual morphometric globes can be used for geological and geomorphological studies of Mars and the Moon at the global, continental, and regional scales.

关键词： Astronomy computational geometry and object modeling Earth and atmospheric sciences Three-dimensional graphics and realism

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Defining, contouring, and visualizing scalar functions on point-sampled surfaces

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COMPUTER-AIDED DESIGN 2011年第3期43卷 227-246页

作者： Patane, Giuseppe Falcidieno, Bianca CNR Ist Matemat Applicata & Tecnol Informat I-16149 Genoa Italy

This paper addresses the definition, contouring, and visualization of scalar functions on unorganized point sets, which are sampled from a surface in 3D space;the proposed framework builds on moving least-squares techniques and implicit modeling. Given a scalar function f : P -> R, defined on a point set P, the idea behind our approach is to exploit the local connectivity structure of the k-nearest neighbor graph of P and mimic the contouring of scalar functions defined on triangle meshes. Moving least-squares and implicit modeling techniques are used to extend f from P to the surface M underlying P. To this end, we compute an analytical approximation (f) over tilde of f that allows us to provide an exact differential analysis of (f) over tilde, draw its iso-contours, visualize its behavior on and around M, and approximate its critical points. We also compare moving least-squares and implicit techniques for the definition of the scalar function underlying f and discuss their numerical stability and approximation accuracy. Finally, the proposed framework is a starting point to extend those processing techniques that build on the analysis of scalar functions on 2-manifold surfaces to point sets. (c) 2010 Elsevier Ltd. All rights reserved.

关键词： Approximation of surfaces and contours Nearest neighbor graph Graph algorithms Point-sampled geometry Topological and shape modeling computational geometry and object modeling

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LFS-Aware Surface Reconstruction From Unoriented 3D Point Clouds

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IEEE TRANSACTIONS ON MULTIMEDIA 2024年 26卷 11415-11427页

作者： Fu, Rao Hormann, Kai Alliez, Pierre INRIA F-06902 Sohia Antipolis France Geometry Factory F-06560 Antibes France Univ Svizzera Italiana USI CH-6900 Lugano Switzerland

We present a novel approach for generating isotropic surface triangle meshes directly from unoriented 3D point clouds, with the mesh density adapting to the estimated local feature size (LFS). Popular reconstruction pipelines first reconstruct a dense mesh from the input point cloud and then apply remeshing to obtain an isotropic mesh. The sequential pipeline makes it hard to find a lower-density mesh while preserving more details. Instead, our approach reconstructs both an implicit function and an LFS-aware mesh sizing function directly from the input point cloud, which is then used to produce the final LFS-aware mesh without remeshing. We combine local curvature radius and shape diameter to estimate the LFS directly from the input point clouds. Additionally, we propose a new mesh solver to solve an implicit function whose zero level set delineates the surface without requiring normal orientation. The added value of our approach is generating isotropic meshes directly from 3D point clouds with an LFS-aware density, thus achieving a trade-off between geometric detail and mesh complexity. Our experiments also demonstrate the robustness of our method to noise, outliers, and missing data and can preserve sharp features for CAD point clouds.

关键词： Surface reconstruction Point cloud compression Three-dimensional displays Shape Estimation Surface fitting Scalability I.3.5 [Computing methodologies] computer graphics computational geometry and object modeling

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Streaming simplification of tetrahedral meshes

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IEEE TRANSACTIONS ON VISUALIZATION AND COMPUTER GRAPHICS 2007年第1期13卷 145-155页

作者： Vo, Huy T. Callahan, Steven P. Lindstrom, Peter Pascucci, Valerio Silva, Claudio T. Sci Comp & Imaging Inst Salt Lake City UT 84112 USA Lawrence Livermore Natl Lab Ctr Appl Sci Comp Livermore CA 94551 USA Univ Utah Sch Comp Salt Lake City UT 84112 USA

Unstructured tetrahedral meshes are commonly used in scientific computing to represent scalar, vector, and tensor fields in three dimensions. Visualization of these meshes can be difficult to perform interactively due to their size and complexity. By reducing the size of the data, we can accomplish real-time visualization necessary for scientific analysis. We propose a two-step approach for streaming simplification of large tetrahedral meshes. Our algorithm arranges the data on disk in a streaming, I/O-efficient format that allows coherent access to the tetrahedral cells. A quadric-based simplification is sequentially performed on small portions of the mesh in-core. Our output is a coherent streaming mesh which facilitates future processing. Our technique is fast, produces high quality approximations, and operates out-of-core to process meshes too large for main memory.

关键词： computational geometry and object modeling out-of-core algorithms streaming algorithms mesh simplification large meshes tetrahedral meshes

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Projective Feature Learning for 3D Shapes with Multi-View Depth Images

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COMPUTER GRAPHICS FORUM 2015年第7期34卷 1-11页

作者： Xie, Zhige Xu, Kai Shan, Wen Liu, Ligang Xiong, Yueshan Huang, Hui SIAT Shenzhen VisuCA Key Lab Shenzhen Peoples R China Natl Univ Def Technol Sch Comp Beijing Peoples R China Univ Sci & Technol China Sch Math Sci Beijing Peoples R China

Feature learning for 3D shapes is challenging due to the lack of natural paramterization for 3D surface models. We adopt the multi-view depth image representation and propose Multi-View Deep Extreme Learning Machine (MVD-ELM) to achieve fast and quality projective feature learning for 3D shapes. In contrast to existing multi-view learning approaches, our method ensures the feature maps learned for different views are mutually dependent via shared weights and in each layer, their unprojections together form a valid 3D reconstruction of the input 3D shape through using normalized convolution kernels. These lead to a more accurate 3D feature learning as shown by the encouraging results in several applications. Moreover, the 3D reconstruction property enables clear visualization of the learned features, which further demonstrates the meaningfulness of our feature learning.

关键词： Categories and Subject Descriptors (according to ACM CCS) I.3.5 [Computer Graphics]: modeling&mdash computational geometry and object modeling

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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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Efficient direct rendering of deforming surfaces via shared subdivision trees

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COMPUTER-AIDED DESIGN 2015年第0期58卷 132-140页

作者： Liu, Fuchang Martin, Tobias Yeung, Sai-Kit Gross, Markus Hangzhou Normal Univ Hangzhou 311121 Zhejiang Peoples R China Swiss Fed Inst Technol Zurich Switzerland Singapore Univ Technol & Design Singapore Singapore

In this paper, we present a subdivision-based approach to rasterize implicit surfaces embedded in volumetric Bezier patches undergoing a nonlinear deformation. Subdividing a given patch into simpler patches to perform the surface rasterization task is numerically robust, and allows guaranteeing visual accuracy even in the presence of geometric degeneracies. However, due to its memory requirements and slow convergence rates, subdivision is challenging to be used in an interactive environment. Unlike previous methods employing subdivision, our approach is based on the idea where for a given patch only one subdivision tree is maintained and shared among pixels. Furthermore, as the geometry of the object changes from frame to frame, a flexible data structure is proposed to manage the geometrically varying Bezier patches. The resulting algorithm is general and maps well to parallel computing platforms such as CUDA. We demonstrate on a variety of representative graphics and visualization examples that our GPU scheme scales well and achieves up to real-time performance on consumer-level graphics cards by guaranteeing visual accuracy. (C) 2014 Elsevier Ltd. All rights reserved.

关键词： Isosurface visualization GPU rendering computational geometry and object modeling

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Freeform extrusion by sketched input

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COMPUTERS & GRAPHICS-UK 2003年第2期27卷 255-263页

作者： Wang, CCL Yuen, MMF Hong Kong Univ Sci & Technol Dept Mech Engn Kowloon Hong Kong Peoples R China

This paper presents a sketch-based mesh extrusion method, which is useful for intuitive, efficient geometric modeling of freeform polygonal objects. With our method, the user can extrude either a closed or open surface from the surface or the boundary of a given mesh by sketched input. Thus, compared to earlier methods, our method provides more flexibility for solving surface modeling problems. Our mesh extrusion algorithm consists of four steps: (1) create a base curve;(2) project extruding strokes;(3) sweep a base curve;and (4) sew adjacent curves. At the end of this paper, examples of our mesh extrusion implementation are shown to demonstrate its functionality. Our freeform extrusion has been implemented as a part of our sketch-based modeling system, and the mesh extrusion can be completed in real time on a standard PC. (C) 2003 Elsevier Science Ltd. All rights reserved.

关键词： computational geometry and object modeling interaction styles computer-aided design

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