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Visualization and Computer Graphics, IEEE Transactions on

Issue 3 • Date May-June 2009

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Displaying Results 1 - 18 of 18
  • [Front cover]

    Publication Year: 2009 , Page(s): c1
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  • [Inside front cover]

    Publication Year: 2009 , Page(s): c2
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  • Guest Editor's Introduction: Special Section on the IEEE Virtual Reality Conference (VR)

    Publication Year: 2009 , Page(s): 353 - 354
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  • Multithreaded Hybrid Feature Tracking for Markerless Augmented Reality

    Publication Year: 2009 , Page(s): 355 - 368
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3152 KB) |  | HTML iconHTML  

    We describe a novel markerless camera tracking approach and user interaction methodology for augmented reality (AR) on unprepared tabletop environments. We propose a real-time system architecture that combines two types of feature tracking. Distinctive image features of the scene are detected and tracked frame-to-frame by computing optical flow. In order to achieve real-time performance, multiple operations are processed in a synchronized multi-threaded manner: capturing a video frame, tracking features using optical flow, detecting distinctive invariant features, and rendering an output frame. We also introduce user interaction methodology for establishing a global coordinate system and for placing virtual objects in the AR environment by tracking a user's outstretched hand and estimating a camera pose relative to it. We evaluate the speed and accuracy of our hybrid feature tracking approach, and demonstrate a proof-of-concept application for enabling AR in unprepared tabletop environments, using bare hands for interaction. View full abstract»

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  • Mixed Reality Humans: Evaluating Behavior, Usability, and Acceptability

    Publication Year: 2009 , Page(s): 369 - 382
    Cited by:  Papers (8)
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1749 KB) |  | HTML iconHTML  

    This paper presents mixed reality humans (MRHs), a new type of embodied agent enabling touch-driven communication. Affording touch between human and agent allows MRHs to simulate interpersonal scenarios in which touch is crucial. Two studies provide initial evaluation of user behavior with a MRH patient and the usability and acceptability of a MRH patient for practice and evaluation of medical students' clinical skills. In Study I (n = 8) it was observed that students treated MRHs as social actors more than students in prior interactions with virtual human patients (n = 27), and used interpersonal touch to comfort and reassure the MRH patient similarly to prior interactions with human patients (n = 76). In the within-subjects Study II (n = 11), medical students performed a clinical breast exam on each of a MRH and human patient. Participants performed equivalent exams with the MRH and human patients, demonstrating the usability of MRHs to evaluate students' exam skills. The acceptability of the MRH patient for practicing exam skills was high as students rated the experience as believable and educationally beneficial. Acceptability was improved from Study I to Study II due to an increase in the MRH's visual realism, demonstrating that visual realism is critical for simulation of specific interpersonal scenarios. View full abstract»

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  • Evaluation of Reorientation Techniques and Distractors for Walking in Large Virtual Environments

    Publication Year: 2009 , Page(s): 383 - 394
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2002 KB) |  | HTML iconHTML  

    Virtual environments (VEs) that use a real-walking locomotion interface have typically been restricted in size to the area of the tracked lab space. Techniques proposed to lift this size constraint, enabling real walking in VEs that are larger than the tracked lab space, all require reorientation techniques (ROTs) in the worst-case situation-when a user is close to walking out of the tracked space. We propose a new ROT using visual and audial distractors-objects in the VE that the user focuses on while the VE rotates-and compare our method to current ROTs through three user studies. ROTs using distractors were preferred and ranked more natural by users. Our findings also suggest that improving visual realism and adding sound increased a user's feeling of presence. Users were also less aware of the rotating VE when ROTs with distractors were used. View full abstract»

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  • Semiautomatic Transfer Function Initialization for Abdominal Visualization Using Self-Generating Hierarchical Radial Basis Function Networks

    Publication Year: 2009 , Page(s): 395 - 409
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3357 KB) |  | HTML iconHTML  

    Being a tool that assigns optical parameters used in interactive visualization, transfer functions (TF) have important effects on the quality of volume rendered medical images. Unfortunately, finding accurate TFs is a tedious and time consuming task because of the trade off between using extensive search spaces and fulfilling the physician's expectations with interactive data exploration tools and interfaces. By addressing this problem, we introduce a semi-automatic method for initial generation of TFs. The proposed method uses a self generating hierarchical radial basis function network to determine the lobes of a volume histogram stack (VHS) which is introduced as a new domain by aligning the histograms of slices of a image series. The new self generating hierarchical design strategy allows the recognition of suppressed lobes corresponding to suppressed tissues and representation of the overlapping regions which are parts of the lobes but can not be represented by the Gaussian bases in VHS. Moreover, approximation with a minimum set of basis functions provides the possibility of selecting and adjusting suitable units to optimize the TF. Applications on different CT/MR data sets show enhanced rendering quality and reduced optimization time in abdominal studies. View full abstract»

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  • A Novel Visualization Technique for Electric Power Grid Analytics

    Publication Year: 2009 , Page(s): 410 - 423
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3990 KB) |  | HTML iconHTML  

    The application of information visualization holds tremendous promise for the electric power industry, but its potential has so far not been sufficiently exploited by the visualization community. Prior work on visualizing electric power systems has been limited to depicting raw or processed information on top of a geographic layout. Little effort has been devoted to visualizing the physics of the power grids, which ultimately determines the condition and stability of the electricity infrastructure. Based on this assessment, we developed a novel visualization system prototype, GreenGrid, to explore the planning and monitoring of the North American Electricity Infrastructure. The paper discusses the rationale underlying the GreenGrid design, describes its implementation and performance details, and assesses its strengths and weaknesses against the current geographic-based power grid visualization. We also present a case study using GreenGrid to analyze the information collected moments before the last major electric blackout in the Western United States and Canada, and a usability study to evaluate the practical significance of our design in simulated real-life situations. Our result indicates that many of the disturbance characteristics can be readily identified with the proper form of visualization. View full abstract»

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  • Visualization of Simulated Urban Spaces: Inferring Parameterized Generation of Streets, Parcels, and Aerial Imagery

    Publication Year: 2009 , Page(s): 424 - 435
    Cited by:  Papers (11)
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4356 KB) |  | HTML iconHTML  

    Urban simulation models and their visualization are used to help regional planning agencies evaluate alternative transportation investments, land use regulations, and environmental protection policies. Typical urban simulations provide spatially distributed data about number of inhabitants, land prices, traffic, and other variables. In this article, we build on a synergy of urban simulation, urban visualization, and computer graphics to automatically infer an urban layout for any time step of the simulation sequence. In addition to standard visualization tools, our method gathers data of the original street network, parcels, and aerial imagery and uses the available simulation results to infer changes to the original urban layout and produce a new and plausible layout for the simulation results. In contrast with previous work, our approach automatically updates the layout based on changes in the simulation data and thus can scale to a large simulation over many years. The method in this article offers a substantial step forward in building integrated visualization and behavioral simulation systems for use in community visioning, planning, and policy analysis. We demonstrate our method on several real cases using a 200-Gbyte database for a 16,300 km2 area surrounding Seattle. View full abstract»

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  • Equalizer: A Scalable Parallel Rendering Framework

    Publication Year: 2009 , Page(s): 436 - 452
    Cited by:  Papers (22)
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3750 KB) |  | HTML iconHTML  

    Continuing improvements in CPU and GPU performances as well as increasing multi-core processor and cluster-based parallelism demand for flexible and scalable parallel rendering solutions that can exploit multipipe hardware accelerated graphics. In fact, to achieve interactive visualization, scalable rendering systems are essential to cope with the rapid growth of data sets. However, parallel rendering systems are non-trivial to develop and often only application specific implementations have been proposed. The task of developing a scalable parallel rendering framework is even more difficult if it should be generic to support various types of data and visualization applications, and at the same time work efficiently on a cluster with distributed graphics cards. In this paper we introduce a novel system called Equalizer, a toolkit for scalable parallel rendering based on OpenGL which provides an application programming interface (API) to develop scalable graphics applications for a wide range of systems ranging from large distributed visualization clusters and multi-processor multipipe graphics systems to single-processor single-pipe desktop machines. We describe the system architecture, the basic API, discuss its advantages over previous approaches, present example configurations and usage scenarios as well as scalability results. View full abstract»

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  • Real-Time Depth-of-Field Rendering Using Anisotropically Filtered Mipmap Interpolation

    Publication Year: 2009 , Page(s): 453 - 464
    Cited by:  Papers (7)  |  Patents (1)
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2661 KB) |  | HTML iconHTML  

    This article presents a real-time GPU-based post-filtering method for rendering acceptable depth-of-field effects suited for virtual reality. Blurring is achieved by nonlinearly interpolating mipmap images generated from a pinhole image. Major artifacts common in the post-filtering techniques such as bilinear magnification artifact, intensity leakage, and blurring discontinuity are practically eliminated via magnification with a circular filter, anisotropic mipmapping, and smoothing of blurring degrees. The whole framework is accelerated using GPU programs for constant and scalable real-time performance required for virtual reality. We also compare our method to recent GPU-based methods in terms of image quality and rendering performance. View full abstract»

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  • An Adaptive Correspondence Algorithm for Modeling Scenes with Strong Interreflections

    Publication Year: 2009 , Page(s): 465 - 480
    Cited by:  Papers (9)
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4910 KB) |  | HTML iconHTML  

    Modeling real-world scenes, beyond diffuse objects, plays an important role in computer graphics, virtual reality, and other commercial applications. One active approach is projecting binary patterns in order to obtain correspondence and reconstruct a densely sampled 3D model. In such structured-light systems, determining whether a pixel is directly illuminated by the projector is essential to decoding the patterns. When a scene has abundant indirect light, this process is especially difficult. In this paper, we present a robust pixel classification algorithm for this purpose. Our method correctly establishes the lower and upper bounds of the possible intensity values of an illuminated pixel and of a non-illuminated pixel. Based on the two intervals, our method classifies a pixel by determining whether its intensity is within one interval but not in the other. Our method performs better than standard method due to the fact that it avoids gross errors during decoding process caused by strong inter-reflections. For the remaining uncertain pixels, we apply an iterative algorithm to reduce the inter-reflection within the scene. Thus, more points can be decoded and reconstructed after each iteration. Moreover, the iterative algorithm is carried out in an adaptive fashion for fast convergence. View full abstract»

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  • Indexing and Retrieving Motions of Characters in Close Contact

    Publication Year: 2009 , Page(s): 481 - 492
    Cited by:  Papers (9)
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1791 KB) |  | HTML iconHTML  

    Human motion indexing and retrieval are important for animators due to the need to search for motions in the database which can be blended and concatenated. Most of the previous researches of human motion indexing and retrieval compute the Euclidean distance of joint angles or joint positions. Such approaches are difficult to apply for cases in which multiple characters are closely interacting with each other, as the relationships of the characters are not encoded in the representation. In this research, we propose a topology-based approach to index the motions of two human characters in close contact. We compute and encode how the two bodies are tangled based on the concept of rational tangles. The encoded relationships, which we define as TangleList, are used to determine the similarity of the pairs of postures. Using our method, we can index and retrieve motions such as one person piggy-backing another, one person assisting another in walking, and two persons dancing/wrestling. Our method is useful to manage a motion database of multiple characters. We can also produce motion graph structures of two characters closely interacting with each other by interpolating and concatenating topologically similar postures and motion clips, which are applicable to 3D computer games and computer animation. View full abstract»

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  • Direct Forcing for Lagrangian Rigid-Fluid Coupling

    Publication Year: 2009 , Page(s): 493 - 503
    Cited by:  Papers (14)
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1292 KB) |  | HTML iconHTML  

    We propose a novel boundary handling algorithm for particle-based fluids. Based on a predictor-corrector scheme for both velocity and position, one- and two-way coupling with rigid bodies can be realized. The proposed algorithm offers significant improvements over existing penalty-based approaches. Different slip conditions can be realized and non-penetration is enforced. Direct forcing is employed to meet the desired boundary conditions and to ensure valid states after each simulation step. We have performed various experiments in 2D and 3D. They illustrate one- and two-way coupling of rigid bodies and fluids, the effects of hydrostatic and dynamic forces on a rigid body as well as different slip conditions. Numerical experiments and performance measurements are provided. View full abstract»

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  • Computing Teichmuller Shape Space

    Publication Year: 2009 , Page(s): 504 - 517
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4256 KB) |  | HTML iconHTML  

    Shape indexing, classification, and retrieval are fundamental problems in computer graphics. This work introduces a novel method for surface indexing and classification based on Teichmuller theory. The Teichmuller space for surfaces with the same topology is a finite dimensional manifold, where each point represents a conformal equivalence class, a curve represents a deformation process from one class to the other. We apply Teichmuller space coordinates as shape descriptors, which are succinct, discriminating and intrinsic; invariant under the rigid motions and scalings, insensitive to resolutions. Furthermore, the method has solid theoretic foundation, and the computation of Teichmuller coordinates is practical, stable and efficient. This work focuses on the surfaces with negative Euler numbers, which have a unique conformal Riemannian metric with -1 Gaussian curvature. The coordinates which we will compute are the lengths of a special set of geodesics under this special metric. The metric can be obtained by the curvature flow algorithm, the geodesics can be calculated using algebraic topological method. We tested our method extensively for indexing and comparison of about one hundred of surfaces with various topologies, geometries and resolutions. The experimental results show the efficacy and efficiency of the length coordinate of the Teichmuller space. View full abstract»

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  • Quasi-Developable Mesh Surface Interpolation via Mesh Deformation

    Publication Year: 2009 , Page(s): 518 - 528
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2756 KB) |  | HTML iconHTML  

    We present a new algorithm for finding a most "developable" smooth mesh surface to interpolate a given set of arbitrary points or space curves. Inspired by the recent progress in mesh editing that employs the concepts of preserving the Laplacian coordinates and handle-based shape editing, we formulate the interpolation problem as a mesh deformation process that transforms an initial developable mesh surface, such as a planar figure, to a final mesh surface that interpolates the given points and/or curves. During the deformation, the developability of the intermediate mesh is maintained by means of preserving the zero-valued Gaussian curvature on the mesh. To treat the high nonlinearity of the geometric constrains owing to the preservation of Gaussian curvature, we linearize those nonlinear constraints using Taylor expansion and eventually construct a sparse and over-determined linear system which is subsequently solved by a robust least-squares solution. By iteratively performing this procedure, the initial mesh is gradually and smoothly "dragged" to the given points and/or curves. The initial experimental data has shown some promising aspects of the proposed algorithm as a general quasi-developable surface interpolation tool. View full abstract»

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  • TVCG Information for authors

    Publication Year: 2009 , Page(s): c3
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  • [Back cover]

    Publication Year: 2009 , Page(s): c4
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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.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Leila De Floriani
Department of Computer Science, Bioengineering, Robotics and Systems Engineering
University of Genova
16146 Genova (Italy)
ldf4tvcg@umiacs.umd.edu