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Visualization and Computer Graphics, IEEE Transactions on

Issue 9 • Date Sept. 1 2014

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Displaying Results 1 - 10 of 10
  • Data-Driven Synthetic Modeling of Trees

    Page(s): 1214 - 1226
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2034 KB) |  | HTML iconHTML  

    In this paper, we develop a data-driven technique to model trees from a single laser scan. A multi-layer representation of the tree structure is proposed to guide the modeling process. In this process, a marching cylinder algorithm is first developed to construct visible branches from the laser scan data. Three levels of crown feature points are then extracted from the scan data to synthesize three layers of non-visible branches. Based on the hierarchical particle flow technique, the branch synthesis method has the advantage of producing visually convincing tree models that are consistent with scan data. User intervention is extremely limited. The robustness of this technique has been validated on both conifer and broadleaf trees. View full abstract»

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  • Direct Isosurface Ray Casting of NURBS-Based Isogeometric Analysis

    Page(s): 1227 - 1240
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1601 KB) |  | HTML iconHTML  

    In NURBS-based isogeometric analysis, the basis functions of a 3D model's geometric description also form the basis for the solution space of variational formulations of partial differential equations. In order to visualize the results of a NURBS-based isogeometric analysis, we developed a novel GPU-based multi-pass isosurface visualization technique which performs directly on an equivalent rational Bézier representation without the need for discretization or approximation. Our approach utilizes rasterization to generate a list of intervals along the ray that each potentially contain boundary or isosurface intersections. Depth-sorting this list for each ray allows us to proceed in front-to-back order and enables early ray termination. We detect multiple intersections of a ray with the higher-order surface of the model using a sampling-based root-isolation method. The model's surfaces and the isosurfaces always appear smooth, independent of the zoom level due to our pixel-precise processing scheme. Our adaptive sampling strategy minimizes costs for point evaluations and intersection computations. The implementation shows that the proposed approach interactively visualizes volume meshes containing hundreds of thousands of Bézier elements on current graphics hardware. A comparison to a GPU-based ray casting implementation using spatial data structures indicates that our approach generally performs significantly faster while being more accurate. View full abstract»

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  • Drawing Road Networks with Mental Maps

    Page(s): 1241 - 1252
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2750 KB) |  | HTML iconHTML  

    Tourist and destination maps are thematic maps designed to represent specific themes in maps. The road network topologies in these maps are generally more important than the geometric accuracy of roads. A road network warping method is proposed to facilitate map generation and improve theme representation in maps. The basic idea is deforming a road network to meet a user-specified mental map while an optimization process is performed to propagate distortions originating from road network warping. To generate a map, the proposed method includes algorithms for estimating road significance and for deforming a road network according to various geometric and aesthetic constraints. The proposed method can produce an iconic mark of a theme from a road network and meet a user-specified mental map. Therefore, the resulting map can serve as a tourist or destination map that not only provides visual aids for route planning and navigation tasks, but also visually emphasizes the presentation of a theme in a map for the purpose of advertising. In the experiments, the demonstrations of map generations show that our method enables map generation systems to generate deformed tourist and destination maps efficiently. View full abstract»

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  • Efficient Structure-Aware Image Smoothingby Local Extrema on Space-Filling Curve

    Page(s): 1253 - 1265
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2477 KB) |  | HTML iconHTML  

    This paper presents a novel image smoothing approach using a space-filling curve as the reduced domain to perform separation of edges and details. This structure-aware smoothing effect is achieved by modulating local extrema after empirical mode decomposition; it is highly effective and efficient since it is implemented on a one-dimensional curve instead of a two-dimensional image grid. To overcome edge staircase-like artifacts caused by a neighborhood deficiency in domain reduction, we next use a joint contrast-based filter to consolidate edge structures in image smoothing. The adoption of dimensional reduction makes our smoothing approach distinct for two reasons. First, overall structure-awareness is improved as more extrema are exploited to locate the salient edges and details. Second, envelope computation for local extrema is made much fast by using explicit interpolants on the curve. Moreover, our approach is simple and very easy to implement in practice. Experimental results demonstrate the merit of our approach, which outperforms previous state-of-the-art methods, for a variety of image processing tasks. View full abstract»

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  • Implicit Multibody Penalty-BasedDistributed Contact

    Page(s): 1266 - 1279
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1196 KB) |  | HTML iconHTML  

    The penalty method is a simple and popular approach to resolving contact in computer graphics and robotics. Penalty-based contact, however, suffers from stability problems due to the highly variable and unpredictable net stiffness, and this is particularly pronounced in simulations with time-varying distributed geometrically complex contact. We employ semi-implicit integration, exact analytical contact gradients, symbolic Gaussian elimination and a SVD solver to simulate stable penalty-based frictional contact with large, time-varying contact areas, involving many rigid objects and articulated rigid objects in complex conforming contact and self-contact. We also derive implicit proportional-derivative control forces for real-time control of articulated structures with loops. We present challenging contact scenarios such as screwing a hexbolt into a hole, bowls stacked in perfectly conforming configurations, and manipulating many objects using actively controlled articulated mechanisms in real time. View full abstract»

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  • Large-Scale Point-Cloud Visualization through Localized Textured Surface Reconstruction

    Page(s): 1280 - 1292
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1830 KB) |  | HTML iconHTML  

    In this paper, we introduce a novel scene representation for the visualization of large-scale point clouds accompanied by a set of high-resolution photographs. Many real-world applications deal with very densely sampled point-cloud data, which are augmented with photographs that often reveal lighting variations and inaccuracies in registration. Consequently, the high-quality representation of the captured data, i.e., both point clouds and photographs together, is a challenging and time-consuming task. We propose a two-phase approach, in which the first (preprocessing) phase generates multiple overlapping surface patches and handles the problem of seamless texture generation locally for each patch. The second phase stitches these patches at render-time to produce a high-quality visualization of the data. As a result of the proposed localization of the global texturing problem, our algorithm is more than an order of magnitude faster than equivalent mesh-based texturing techniques. Furthermore, since our preprocessing phase requires only a minor fraction of the whole data set at once, we provide maximum flexibility when dealing with growing data sets. View full abstract»

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  • Making Graphical Information Visible in Real Shadows on Interactive Tabletops

    Page(s): 1293 - 1302
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (891 KB) |  | HTML iconHTML  

    We introduce a shadow-based interface for interactive tabletops. The proposed interface allows a user to browse graphical information by casting the shadow of his/her body, such as a hand, on a tabletop surface. Central to our technique is a new optical design that utilizes polarization in addition to the additive nature of light so that the desired graphical information is displayed only in a shadow area on a tabletop surface. In other words, our technique conceals the graphical information on surfaces other than the shadow area, such as the surface of the occluder and non-shadow areas on the tabletop surface. We combine the proposed shadow-based interface with a multi-touch detection technique to realize a novel interaction technique for interactive tabletops. We implemented a prototype system and conducted proof-of-concept experiments along with a quantitative evaluation to assess the feasibility of the proposed optical design. Finally, we showed implemented application systems of the proposed shadow-based interface. View full abstract»

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  • Object Movements Synopsis viaPart Assembling and Stitching

    Page(s): 1303 - 1315
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2072 KB) |  | HTML iconHTML  

    Video synopsis aims at removing video's less important information, while preserving its key content for fast browsing, retrieving, or efficient storing. Previous video synopsis methods, including frame-based and object-based approaches that remove valueless whole frames or combine objects from time shots, cannot handle videos with redundancies existing in the movements of video object. In this paper, we present a novel part-based object movements synopsis method, which can effectively compress the redundant information of a moving video object and represent the synopsized object seamlessly. Our method works by part-based assembling and stitching. The object movement sequence is first divided into several part movement sequences. Then, we optimally assemble moving parts from different part sequences together to produce an initial synopsis result. The optimal assembling is formulated as a part movement assignment problem on a Markov Random Field (MRF), which guarantees the most important moving parts are selected while preserving both the spatial compatibility between assembled parts and the chronological order of parts. Finally, we present a non-linear spatiotemporal optimization formulation to stitch the assembled parts seamlessly, and achieve the final compact video object synopsis. The experiments on a variety of input video objects have demonstrated the effectiveness of the presented synopsis method. View full abstract»

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  • Second-Order Feed-Forward Renderingfor Specular and Glossy Reflections

    Page(s): 1316 - 1329
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1719 KB) |  | HTML iconHTML  

    The feed-forward pipeline based on projection followed by rasterization handles the rays that leave the eye efficiently: these first-order rays are modeled with a simple camera that projects geometry to screen. Second-order rays however, as, for example, those resulting from specular reflections, are challenging for the feed-forward approach. We propose an extension of the feed-forward pipeline to handle second-order rays resulting from specular and glossy reflections. The coherence of second-order rays is leveraged through clustering, the geometry reflected by a cluster is approximated with a depth image, and the color samples captured by the second-order rays of a cluster are computed by intersection with the depth image. We achieve quality specular and glossy reflections at interactive rates in fully dynamic scenes. View full abstract»

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  • Volume Rendering of Curvilinear-Grid Data Using Low-Dimensional Deformation Textures

    Page(s): 1330 - 1343
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1313 KB) |  | HTML iconHTML  

    In this paper, we present a high quality and interactive method for volume rendering curvilinear-grid data sets. This method is based on a two-stage parallel transformation of the sample position into intermediate computational space then into texture space through the use of multiple 1 and 2D deformation textures using hardware acceleration. In this manner, it is possible to render many curvilinear-grid volume data sets at high quality and with a low memory footprint, while taking advantage of modern graphic hardware's tri-linear filtering for the data itself. We also extend our method to handle volume shading. Additionally, we present a comprehensive study and comparisons with previous works, we show improvements both in quality and performance using our technique on multiple curvilinear data sets. View full abstract»

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Aims & Scope

Visualization techniques and methodologies; visualization systems and software; volume visualization; flow visualization; multivariate visualization; modeling and surfaces; rendering; animation; user interfaces; visual progranuning; applications.

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Meet Our Editors

Editor-in-Chief
Ming Lin
Department of Computer Science
University of North Carolina