Computer Graphics Forum

Cover image for Vol. 32 Issue 6

September 2013

Volume 32, Issue 6

Pages i–ii, 1–251

  1. Issue Information

    1. Top of page
    2. Issue Information
    3. Articles
    4. Reports
    5. Erratum
    1. Issue Information (pages i–ii)

      Version of Record online: 13 SEP 2013 | DOI: 10.1111/cgf.12203

  2. Articles

    1. Top of page
    2. Issue Information
    3. Articles
    4. Reports
    5. Erratum
    1. Symmetry in 3D Geometry: Extraction and Applications (pages 1–23)

      Niloy J. Mitra, Mark Pauly, Michael Wand and Duygu Ceylan

      Version of Record online: 4 FEB 2013 | DOI: 10.1111/cgf.12010

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      The concept of symmetry has received significant attention in computer graphics and computer vision research in recent years. Numerous methods have been proposed to find, extract, encode, and exploit geometric symmetries and high-level structural information for a wide variety of geometry processing tasks. This report surveys and classifies recent developments in symmetry detection. We focus on elucidating the key similarities and differences between existing methods to gain a better understanding of a fundamental problem in digital geometry processing and shape understanding in general.

    2. Full Wave Modelling of Light Propagation and Reflection (pages 24–37)

      A. Musbach, G. W. Meyer, F. Reitich and S. H. Oh

      Version of Record online: 4 FEB 2013 | DOI: 10.1111/cgf.12012

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      The propagation and reflection of electromagnetic waves in a three-dimensional environment is simulated, and realistic images are produced using the resulting light distributions and reflectance functions. A finite difference time domain method is employed to advance the electric and magnetic fields in a scene. Surfaces containing wavelength scaled structures are created, the interaction of the electromagnetic waves with these nano-structured materials is calculated, and the sub-surface interference and diffraction effects are modeled. The result is a reflectance function with wavelength composition and spatial distribution properties that could not have been predicted using classic computer graphic ray tracing approaches.

    3. Visualization Mosaics for Multivariate Visual Exploration (pages 38–50)

      S. MacNeil and N. Elmqvist

      Version of Record online: 12 FEB 2013 | DOI: 10.1111/cgf.12013

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      We present a new model for creating composite visualizations of multidimensional datasets using simple visual representations such as point charts, scatterplots, and parallel coordinates as components. Each visual representation is contained in a tile, and the tiles are arranged in a mosaic of views using a space-filling slice-and-dice layout. Tiles can be created, resized, split, or merged using a versatile set of interaction techniques, and the visual representation of individual tiles can also be dynamically changed to another representation. Because each tile is self-contained and independent, it can be implemented in any programming language, on any platform, and using any visual representation.

    4. Quad-Mesh Generation and Processing: A Survey (pages 51–76)

      David Bommes, Bruno Lévy, Nico Pietroni, Enrico Puppo, Claudio Silva, Marco Tarini and Denis Zorin

      Version of Record online: 4 MAR 2013 | DOI: 10.1111/cgf.12014

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      Triangle meshes have been nearly ubiquitous in computer graphics, and a large body of data structures and geometry processing algorithms based on them has been developed in the literature. At the same time, quadrilateral meshes, especially semi-regular ones, have advantages for many applications, and significant progress was made in quadrilateral mesh generation and processing during the last several years. In this survey we discuss the advantages and problems of techniques operating on quadrilateral meshes, including surface analysis and mesh quality, simplification, adaptive refinement, alignment with features, parametrization, and remeshing.

    5. Curve Style Analysis in a Set of Shapes (pages 77–88)

      H. Li, H. Zhang, Y. Wang, J. Cao, A. Shamir and D. Cohen-Or

      Version of Record online: 12 FEB 2013 | DOI: 10.1111/cgf.12015

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      Triangle meshes have been nearly ubiquitous in computer graphics, and a large body of data structures and geometry processing algorithms based on them has been developed in the literature. At the same time, quadrilateral meshes, especially semi-regular ones, have advantages for many applications, and significant progress was made in quadrilateral mesh generation and processing during the last several years. In this survey we discuss the advantages and problems of techniques operating on quadrilateral meshes, including surface analysis and mesh quality, simplification, adaptive refinement, alignment with features, parametrization, and remeshing.

    6. Efficient Non-linear Optimization via Multi-scale Gradient Filtering (pages 89–100)

      Tobias Martin, Pushkar Joshi, Miklós Bergou and Nathan Carr

      Version of Record online: 7 APR 2013 | DOI: 10.1111/cgf.12019

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      We present a method for accelerating the convergence of continuous nonlinear shape optimization algorithms. We start with a general method for constructing gradient vector fields on a manifold, and we analyze this method from a signal processing viewpoint. This analysis reveals that we can construct various filters using the Laplace-Beltrami operator of the shape that can effectively separate the components of the gradient at different scales. We use this idea to adaptively change the scale of features being optimized in order to arrive at a solution that is optimal across multiple scales.

    7. Robust Fitting on Poorly Sampled Data for Surface Light Field Rendering and Image Relighting (pages 101–112)

      K. Vanhoey, B. Sauvage, O. Génevaux, F. Larue and J.-M. Dischler

      Version of Record online: 1 APR 2013 | DOI: 10.1111/cgf.12073

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      Generating surface light fields from real acquisition campaigns' data often leads to robustness issues that are due to irregular distribution and sparsity of the photographic sampling. Within this context, we present a robust least-squares-based method for fitting 2D parametric colour functions on sparse and scattered data. Moreover, we provide a statistical analysis to measure the robustness of such fitting approaches. The proposed method allows, on one hand, for high-quality reconstructions in good sampling conditions and, on the other hand, for robust and predictable reconstructions in poor sampling conditions.

    8. Enhancing Bayesian Estimators for Removing Camera Shake (pages 113–125)

      C. Wang, Y. Yue, F. Dong, Y. Tao, X. Ma, G. Clapworthy and X. Ye

      Version of Record online: 18 MAR 2013 | DOI: 10.1111/cgf.12074

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      The aim of removing camera shake is to estimate a sharp version x from a shaken image y when the blur kernel k is unknown. Recent research on this topic evolved through two paradigms called MAP(k) and MAP(x,k). MAP(k) only solves for k by marginalizing the image prior, while MAP(x,k) recovers both x and k by selecting the mode of the posterior distribution. This paper first systematically analyzes the latent limitations of these two estimators through Bayesian analysis. We explain the reason why it is so difficult for image statistics to solve the previously reported MAP(x,k) failure. Then we show that the leading MAP(x,k) methods, which depend on efficient prediction of large step edges, are not robust to natural images due to the diversity of edges. MAP(k), although much more robust to diverse edges, is constrained by two factors: the prior variation over different images, and the ratio between image size and kernel size.

    9. Real-Time Defocus Rendering With Level of Detail and Sub-Sample Blur (pages 126–134)

      Yuna Jeong, Kangtae Kim and Sungkil Lee

      Version of Record online: 25 MAR 2013 | DOI: 10.1111/cgf.12075

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      This paper presents a GPU-based rendering algorithm for real-time defocus blur effects, which significantly improves the accumulation buffering. The algorithm combines three distinctive techniques: (1) adaptive discrete geometric level of detail (LOD), made popping-free by blending visibility samples across the two adjacent geometric levels; (2) adaptive visibility/shading sampling via sample reuse; (3) visibility supersampling via height-field ray casting. All the three techniques are seamlessly integrated to lower the rendering cost of smooth defocus blur with high visibility sampling rates, while maintaining most of the quality of brute-force accumulation buffering.

    10. Analysis and Visualization of Maps Between Shapes (pages 135–145)

      M. Ovsjanikov, M. Ben-Chen, F. Chazal and L. Guibas

      Version of Record online: 27 MAY 2013 | DOI: 10.1111/cgf.12076

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      In this paper we propose a method for analyzing and visualizing individual maps between shapes, or collections of such maps. Our method is based on isolating and highlighting areas where the maps induce significant distortion of a given measure in a multi-scale way. Unlike the majority of prior work which focuses on discovering maps in the context of shape matching, our main focus is on evaluating, analyzing and visualizing a given map, and the distortion(s) it introduces, in an efficient and intuitive way. We are motivated primarily by the fact that most existing metrics for map evaluation are quadratic and expensive to compute in practice, and that current map visualization techniques are suitable primarily for global map understanding, and typically do not highlight areas where the map fails to meet certain quality criteria in a multi-scale way. We propose to address these challenges in a unified way by considering the functional representation of a map, and performing spectral analysis on this representation. In particular, we propose a simple multi-scale method for map evaluation and visualization, which provides detailed multi-scale information about the distortion induced by a map, which can be used alongside existing global visualization techniques.

    11. A Survey of Urban Reconstruction (pages 146–177)

      P. Musialski, P. Wonka, D. G. Aliaga, M. Wimmer, L. van Gool and W. Purgathofer

      Version of Record online: 10 MAY 2013 | DOI: 10.1111/cgf.12077

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      This paper provides a comprehensive overview of urban reconstruction. While there exists a considerable body of literature, this topic is still under active research. The work reviewed in this survey stems from the following three research communities: computer graphics, computer vision and photogrammetry and remote sensing. Our goal is to provide a survey that will help researchers to better position their own work in the context of existing solutions, and to help newcomers and practitioners in computer graphics to quickly gain an overview of this vast field. Further, we would like to bring the mentioned research communities to even more interdisciplinary work, since the reconstruction problem itself is by far not solved.

    12. InK-Compact: In-Kernel Stream Compaction and Its Application to Multi-Kernel Data Visualization on General-Purpose GPUs (pages 178–188)

      D. M. Hughes, I. S. Lim, M. W. Jones, A. Knoll and B. Spencer

      Version of Record online: 12 APR 2013 | DOI: 10.1111/cgf.12083

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      Stream compaction is an important parallel computing primitive that produces a reduced (compacted) output stream consisting of only valid elements from an input stream containing both invalid and valid elements. Computing on this compacted stream rather than the mixed input stream leads to improvements in performance, load balancing, and memory footprint. Stream compaction has numerous applications in a wide range of domains: e.g., deferred shading, isosurface extraction, and surface voxelization in computer graphics and visualization. We present a novel In-Kernel stream compaction method, where compaction is completed before leaving an operating kernel. This contrasts with conventional parallel compaction methods that require leaving the kernel and running a prefix sum kernel followed by a scatter kernel.

    13. Bilateral Maps for Partial Matching (pages 189–200)

      Oliver van Kaick, Hao Zhang and Ghassan Hamarneh

      Version of Record online: 2 APR 2013 | DOI: 10.1111/cgf.12084

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      Feature-driven analysis forms the basis of many shape processing tasks, where detected feature points are characterized by local shape descriptors. Such descriptors have so far been defined to capture regions of interest centered at individual points. Using such regions to compare feature points can be problematic when performing partial shape matching, since the region of interest is typically defined as an isotropic neighborhood around a point, which does not adapt to the geometry of the shape parts. We introduce the bilateral map, a local shape descriptor whose region of interest is defined by two feature points. Compared to the classical descriptor definition using a single point, the bilateral approach exploits the use of a second point to place more constraints on the selection of the spatial context for feature analysis.

    14. Concentric Spherical Representation for Omnidirectional Soft Shadow (pages 201–213)

      Yi Xiao, Chi Sing Leung, Tze Yui Ho, Liang Wan and Tien Tsing Wong

      Version of Record online: 5 APR 2013 | DOI: 10.1111/cgf.12085

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      Soft shadows play an important role in photo-realistic rendering. Although there are many efficient soft shadow algorithms, most of them focus on the one-side light source situation, where a planar light source is on the outside of the scene. In fact, in many situations, such as games, light sources are omnidirectional. They may be surrounded by a number of 3D objects. This paper proposes a soft shadow algorithm for the omnidirectional situation.

    15. Mesh-Free Discrete Laplace–Beltrami Operator (pages 214–226)

      F. Petronetto, A. Paiva, E. S. Helou, D. E. Stewart and L. G. Nonato

      Version of Record online: 7 MAY 2013 | DOI: 10.1111/cgf.12086

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      In this work we propose a new discretization method for the Laplace–Beltrami operator defined on point-based surfaces. In contrast to the existing point-based discretization techniques, our approach does not rely on any triangle mesh structure, turning out truly meshfree. Based on a combination of Smoothed Particle Hydrodynamics and an optimization procedure to estimate area elements, our discretization method results in accurate solutions while still being robust when facing abrupt changes in the density of points. Moreover, the proposed scheme results in numerically stable discrete operators. The effectiveness of the proposed technique is brought to bear in many practical applications.

    16. A Collaborative Digital Pathology System for Multi-Touch Mobile and Desktop Computing Platforms (pages 227–242)

      W. Jeong, J. Schneider, A. Hansen, M. Lee, S. G. Turney, B. E. Faulkner-Jones, J. L. Hecht, R. Najarian, E. Yee, J. W. Lichtman and H. Pfister

      Version of Record online: 13 JUN 2013 | DOI: 10.1111/cgf.12137

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      Collaborative slide image viewing systems are becoming increasingly important in pathology applications such as telepathology and E-learning. Despite rapid advances in computing and imaging technology, current digital pathology systems have limited performance with respect to remote viewing of whole slide images on desktop or mobile computing devices. In this paper we present a novel digital pathology client-server systems that supports collaborative viewing of multi-plane whole slide images over standard networks using multi-touch enabled clients. Our system is built upon a standard HTTP web server and a MySQL database to allow multiple clients to exchange image and metadata concurrently.

  3. Reports

    1. Top of page
    2. Issue Information
    3. Articles
    4. Reports
    5. Erratum
  4. Erratum

    1. Top of page
    2. Issue Information
    3. Articles
    4. Reports
    5. Erratum
    1. You have free access to this content
      Erratum (page 251)

      Version of Record online: 18 MAY 2013 | DOI: 10.1111/cgf.12138

      This article corrects:

      Perceptual Metrics for Static and Dynamic Triangle Meshes

      Vol. 32, Issue 1, 101–125, Version of Record online: 15 JAN 2013

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