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Data streaming in telepresence environments

IEEE TRANSACTIONS ON VISUALIZATION AND COMPUTER graphics 2005年第6期11卷 637-648页

作者： Lamboray, E Würmlin, S Gross, M Cyfex AG CH-8050 Zurich Switzerland ETH Zentrum Comp Graph Lab IFW C25 1 CH-8092 Zurich Switzerland ETH Zentrum Dept Comp Sci Inst Comp Sci IFW D28 1 CH-8092 Zurich Switzerland

In this paper, we discuss data transmission in telepresence environments for collaborative virtual reality applications. We analyze data streams in the context of networked virtual environments and classify them according to their traffic characteristics. Special emphasis is put on geometry-enhanced (3D) video. We review architectures for real-time 3D video pipelines and derive theoretical bounds on the minimal system latency as a function of the transmission and processing delays. Furthermore, we discuss bandwidth issues of differential update coding for 3D video. In our telepresence system - the blue-c - we use a point-based 3D video technology which allows for differentially encoded 3D representations of human users. While we discuss the considerations which lead to the design of our three-stage 3D video pipeline, we also elucidate some critical implementation details regarding decoupling of acquisition, processing and rendering frame rates, and audio/video synchronization. Finally, we demonstrate the communication and networking features of the blue-c system in its full deployment. We show how the system can possibly be controlled to face processing or networking bottlenecks by adapting the multiple system components like audio, application data, and 3D video.

关键词： computer conferencing teleconferencing and videoconferencing distributed/network graphics three-dimensional graphics and realism

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ExploreMaps: Efficient construction and ubiquitous exploration of panoramic view graphs of complex 3D environments

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COMPUTER graphics FORUM 2014年第2期33卷 459-468页

作者： Di Benedetto, M. Ganovelli, F. Rodriguez, M. Balsa Villanueva, A. Jaspe Scopigno, R. Gobbetti, E. CNR ISTI Visual Comp Grp I-00185 Rome Italy

We introduce a novel efficient technique for automatically transforming a generic renderable 3D scene into a simple graph representation named ExploreMaps, where nodes are nicely placed point of views, called probes, and arcs are smooth paths between neighboring probes. Each probe is associated with a panoramic image enriched with preferred viewing orientations, and each path with a panoramic video. Our GPU-accelerated unattended construction pipeline distributes probes so as to guarantee coverage of the scene while accounting for perceptual criteria before finding smooth, good looking paths between neighboring probes. Images and videos are precomputed at construction time with off-line photorealistic rendering engines, providing a convincing 3D visualization beyond the limits of current real-time graphics techniques. At run-time, the graph is exploited both for creating automatic scene indexes and movie previews of complex scenes and for supporting interactive exploration through a low-DOF assisted navigation interface and the visual indexing of the scene provided by the selected viewpoints. Due to negligible CPU overhead and very limited use of GPU functionality, real-time performance is achieved on emerging web-based environments based on WebGL even on low-powered mobile devices.

关键词： Categories and Subject Descriptors (according to ACM CCS): Computer graphics [I.3.2]: graphics Systems&mdash distributed/network graphics Computer graphics [I.3.7]: Three-Dimensional graphics and Realism&mdash

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Unsupervised learning applied to progressive compression of time-dependent geometry

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COMPUTERS & graphics-UK 2005年第3期29卷 451-461页

作者： Baby, T Kim, Y Varshney, A Univ Maryland Dept Comp Sci College Pk MD 20742 USA

We propose a new approach to progressively compress time-dependent geometry. Our approach exploits correlations in motion vectors to achieve better compression. We use unsupervised learning techniques to detect good clusters of motion vectors. For each detected cluster, we build a hierarchy of motion vectors using pairwise agglomerative clustering, and succinctly encode the hierarchy using entropy encoding. We demonstrate our approach on a client-server system that we have built for downloading time-dependent geometry. (c) 2005 Elsevier Ltd. All rights reserved.

关键词： distributed/network graphics pattern recognition clustering algorithms

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The StarCAVE, a third-generation CAVE and virtual reality OptIPortal

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FUTURE GENERATION COMPUTER SYSTEMS-THE INTERNATIONAL JOURNAL OF ESCIENCE 2009年第2期25卷 169-178页

作者： DeFanti, Thomas A. Dawe, Gregory Sandin, Daniel J. Schulze, Jurgen P. Otto, Peter Girado, Javier Kuester, Falko Smarr, Larry Rao, Ramesh Univ Calif San Diego Calif Inst Telecommun & Informat Technol Calit2 La Jolla CA 92093 USA Univ Illinois EVL Chicago IL USA

A room-sized, walk-in virtual reality (VR) display is to a typical computer screen what a supercomputer is to a laptop computer. It is a vastly more complex system to design, house, optimize, make usable, and maintain. 17 years of designing and implementing room-sized "CAVE" VR systems have led to significant new advances in visual and audio Fidelity. CAVEs are a challenge to construct because their hundreds of constituent components are mostly adapted off-the-shelf technologies that were designed for other uses. The integration of these components and the building of certain critical custom parts like screens involve years of research and development for each new generation of CAVEs. The difficult issues and compromises achieved and deemed acceptable are of keen interest to the relatively small community of VR experimentalists, but also may be enlightening to a broader group of computer scientists not familiar with the barriers to implementing virtual reality and the technical reasons these barriers exist. The StarCAVE, a 3rd-generation CAVE, is a 5-wall plus floor projected virtual reality room, operating at a combined resolution of similar to 68 million pixels, similar to 34 million pixels per eye, distributed over 15 rear-projected wall screens and 2 down-projected floor screens. The StarCAVE offers 20/40 vision in a fully horizontally enclosed space with a diameter of 3 m and height of 3.5 m. Its 15 wall screens are newly developed 1.3 m x 2 in non-depolarizing high-contrast rear-projection screens, stacked three high, with the bottom and top trapezoidal screens tilted inward by 15 degrees to increase immersion, while reducing stereo ghosting. The non-depolarizing, wear-resistant floor screens are lit from overhead. Digital audio sonification is achieved using surround speakers and wave field synthesis, while user interaction is provided via a wand and multi-camera, wireless tracking system. (C) 2008 Elsevier B.V. All rights reserved.

关键词： CAVE, Computer-supported collaborative work distributed/network graphics graphics processors graphics packages Image displays Interactive environments network communication Sonification Teleconferencing Virtual reality

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Adaptive load balancing for raycasting of non-uniformly bricked volumes

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PARALLEL COMPUTING 2007年第6期33卷 406-419页

作者： Mueller, C. Strengert, M. Ertl, T. Univ Stuttgart Inst Visualizat & Interact Syst D-70569 Stuttgart Baden Wurttembe Germany

We describe a sort-last parallel volume rendering system based on single pass volume raycasting performed in the fragment shader unit. The architecture is aimed for displaying data sets that utilize the total distributed texture memory at interactive framerates. We use non-uniform texture bricks that are constructed and distributed by means of a kd-tree to employ object space partitioning. They are further used for implementing empty-space-skipping and a load balancing mechanism, which also makes use of the kd-tree, to increase the overall performance of the rendering system. Performance numbers are given for a mid-range GPU-cluster system consisting of eight render nodes with an Infiniband interconnection. (c) 2007 Elsevier B.V. All rights reserved.

关键词： distributed/network graphics viewing algorithms distributed applications

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Federate resource management in a distributed Virtual Environment

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FUTURE GENERATION COMPUTER SYSTEMS-THE INTERNATIONAL JOURNAL OF ESCIENCE 2010年第3期26卷 308-317页

作者： Belmonte, O. Castaneda, M. Fernandez, D. Gil, J. Aguado, S. Varella, E. Nunez, M. Segarra, J. Univ Jaume 1 Languages & Syst Dept Castellon de La Plana 12071 Spain Univ Oriente Dept Comp Santiago De Cuba Cuba

Most distributed Virtual Environments use ad hoc protocols to share resources and synchronize interaction over a common virtual world. In this scenario, it is difficult to use new virtual reality devices if they have not been taken into account since the beginning. This paper shows how to manage virtual reality devices as federate resources in a virtual world using the HLA-RTI standard architecture. This approach has been used as a framework to build simulators for training workers in civil engineering. (C) 2009 Elsevier B.V. All rights reserved.

关键词： distributed/network graphics Virtual reality Interactive environments Virtual device interfaces

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Improving the performance of distributed virtual environment systems

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IEEE TRANSACTIONS ON PARALLEL AND distributed SYSTEMS 2005年第7期16卷 637-649页

作者： Morillo, P Orduña, JM Fernández, M Duato, J Univ Valencia Dept Informat E-46100 Valencia Spain Univ Politecn Valencia Fac Informat DISCA Valencia 46022 Spain

The last years have witnessed a dramatic growth in the number as well as in the variety of distributed virtual environment systems. These systems allow multiple users, working on different client computers that are interconnected through different networks, to interact in a shared virtual world. One of the key issues in the design of scalable and cost-effective DVE systems is the partitioning problem. This problem consists of efficiently assigning the existing clients to the servers in the system and some techniques have been already proposed for solving it. This paper experimentally analyzes the correlation of the quality function proposed in the literature for solving the partitioning problem with the performance of DVE systems. Since the results show an absence of correlation, we also propose the experimental characterization of DVE systems. The results show that the reason for that absence of correlation is the nonlinear behavior of DVE systems with regard to the number of clients in the system. DVE systems reach saturation when any of the servers reaches 100 percent of CPU utilization. The system performance greatly decreases if this limit is exceeded in any server. Also, as a direct application of these results, we present a partitioning method that is targeted to keep all the servers in the system below a certain threshold value of CPU utilization, regardless of the amount of network traffic. Evaluation results show that the proposed partitioning method can improve DVE system performance, regardless of both the movement pattern of clients and the initial distribution of clients in the virtual world.

关键词： distributed applications distributed/network graphics

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I-SI: Scalable Architecture for Analyzing Latent Topical-Level Information From Social Media Data

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COMPUTER graphics FORUM 2012年第3期31卷 1275-1284页

作者： Wang, X. Dou, W. Ma, Z. Villalobos, J. Chen, Y. Kraft, T. Ribarsky, W. Univ N Carolina Charlotte NC 28223 USA St Lawrence Univ Canton NY USA

We present a general visual analytics architecture that is designed and implemented to effectively analyze unstructured social media data on a large scale. Pipelined on a high-performance cluster configuration, MPI processing, and interactive visual analytics interfaces, our architecture, I-SI, closely integrates data-driven analytical methods and user-centered visual analytics. It creates a coherent analysis environment for identifying event structures, geographical distributions, and key indicators of emerging events. This environment supports monitoring, analyzing, and responding to latent information extracted from social media. We have applied the I-SI architecture to collect social media data, analyze the data on a large scale and uncover the latent social phenomena. To demonstrate the efficacy and applicability of I-SI, we describe several social media use cases in multiple domains that were evaluated by experts. The use cases demonstrate that I-SI can benefit a range of users by constructing meaningful event structures and identifying precursors to critical events within a rich, evolving set of topics.

关键词： I.3.2 [Computer graphics]: graphics Systems&mdash distributed/network graphics

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Streaming HLODs: an out-of-core viewer for network visualization of huge polygon models

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COMPUTERS & graphics-UK 2004年第1期28卷 43-50页

作者： Guthe, M Klein, R Univ Bonn Inst Comp Sci 2 D-53117 Bonn Germany

The constant growth of network and internet availability and speed as well as the increasing power of consumer level graphics hardware have created more and more interest in streaming transmission of three-dimensional data sets. However, since the size of such models is increasing even faster than the transmission or rendering bandwidth and has already exceeded the main memory available in common PCs, we present a combination of quasi view-dependent hierarchical level of detail (HLOD) rendering with priority-based streaming that is capable of rendering highly complex models at a real-time frame rates and high quality even with a low network bandwidth. We show the modifications needed to incorporate the streaming into a recent HLOD rendering system and explore different techniques to reduce the loss of quality compared to local out-of-core rendering. (C) 2003 Elsevier Ltd. All rights reserved.

关键词： distributed/network graphics viewing algorithms compression (coding)

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RBF Volume Ray Casting on Multicore and Manycore CPUs

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COMPUTER graphics FORUM 2014年第3期33卷 71-80页

作者： Knoll, Aaron Wald, Ingo Navratil, Paul Bowen, Anne Reda, Khairi Papka, Michael E. Gaither, Kelly Univ Texas Austin Texas Adv Comp Ctr Austin TX 78712 USA Intel Corp Santa Clara CA 95051 USA Univ Illinois Elect Visualizat Lab Chicago IL USA Argonne Natl Lab Argonne IL 60439 USA

Modern supercomputers enable increasingly large N-body simulations using unstructured point data. The structures implied by these points can be reconstructed implicitly. Direct volume rendering of radial basis function (RBF) kernels in domain-space offers flexible classification and robust feature reconstruction, but achieving performant RBF volume rendering remains a challenge for existing methods on both CPUs and accelerators. In this paper, we present a fast CPU method for direct volume rendering of particle data with RBF kernels. We propose a novel two-pass algorithm: first sampling the RBF field using coherent bounding hierarchy traversal, then subsequently integrating samples along ray segments. Our approach performs interactively for a range of data sets from molecular dynamics and astrophysics up to 82 million particles. It does not rely on level of detail or subsampling, and offers better reconstruction quality than structured volume rendering of the same data, exhibiting comparable performance and requiring no additional preprocessing or memory footprint other than the BVH. Lastly, our technique enables multi-field, multi-material classification of particle data, providing better insight and analysis.

关键词： Categories and Subject Descriptors (according to ACM CCS) I.3.3 [Computer graphics]: Picture/Image Generation&mdash Line and curve generation I.3.7 [Computer graphics]: Three-Dimensional graphics and Realism&mdash Raytracing I.3.2 [Computer graphics]: graphics Systems&mdash distributed/network graphics

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