Streaming of Plants in Distributed Virtual Environments

International audienceJust as in the real world, plants are important objects in virtual world for creating pleasant and realistic environments, especially those involving natural scenes. As such, much effort has been made in realistic modeling of plants. As the trend moves towards networked and distributed virtual environment, however, the current models are inadequate as they are not designed for progressive transmissions. In this paper, we fill in this gap by proposing a progressive representation for plants based on generalized cylinders. To facilitate the transmission of the plants, we quantify the visual contribution of each branch and use this weight in packet scheduling. We show the efficiency of our representations and effectiveness of our packet scheduler through simulations

Streaming instability of slime mold amoebae: An analytical model

During the aggregation of amoebae of the cellular slime mould Dictyostelium, the interaction of chemical waves of the signaling molecule cAMP with cAMP-directed cell movement causes the breakup of a uniform cell layer into branching patterns of cell streams. Recent numerical and experimental investigations emphasize the pivotal role of the cell-density dependence of the chemical wave speed for the occurrence of the streaming instability. A simple, analytically tractable, model of Dictyostelium aggregation is developed to test this idea. The interaction of cAMP waves with cAMP-directed cell movement is studied in the form of coupled dynamics of wave front geometries and cell density. Comparing the resulting explicit instability criterion and dispersion relation for cell streaming with the previous findings of model simulations and numerical stability analyses, a unifying interpretation of the streaming instability as a cAMP wave-driven chemotactic instability is proposed

Streaming visualisation of quantitative mass spectrometry data based on a novel raw signal decomposition method

As data rates rise, there is a danger that informatics for high-throughput LC-MS becomes more opaque and inaccessible to practitioners. It is therefore critical that efficient visualisation tools are available to facilitate quality control, verification, validation, interpretation, and sharing of raw MS data and the results of MS analyses. Currently, MS data is stored as contiguous spectra. Recall of individual spectra is quick but panoramas, zooming and panning across whole datasets necessitates processing/memory overheads impractical for interactive use. Moreover, visualisation is challenging if significant quantification data is missing due to data-dependent acquisition of MS/MS spectra. In order to tackle these issues, we leverage our seaMass technique for novel signal decomposition. LC-MS data is modelled as a 2D surface through selection of a sparse set of weighted B-spline basis functions from an over-complete dictionary. By ordering and spatially partitioning the weights with an R-tree data model, efficient streaming visualisations are achieved. In this paper, we describe the core MS1 visualisation engine and overlay of MS/MS annotations. This enables the mass spectrometrist to quickly inspect whole runs for ionisation/chromatographic issues, MS/MS precursors for coverage problems, or putative biomarkers for interferences, for example. The open-source software is available from http://seamass.net/viz/

Doctor of Philosophy

dissertationInteractive editing and manipulation of digital media is a fundamental component in digital content creation. One media in particular, digital imagery, has seen a recent increase in popularity of its large or even massive image formats. Unfortunately, current systems and techniques are rarely concerned with scalability or usability with these large images. Moreover, processing massive (or even large) imagery is assumed to be an off-line, automatic process, although many problems associated with these datasets require human intervention for high quality results. This dissertation details how to design interactive image techniques that scale. In particular, massive imagery is typically constructed as a seamless mosaic of many smaller images. The focus of this work is the creation of new technologies to enable user interaction in the formation of these large mosaics. While an interactive system for all stages of the mosaic creation pipeline is a long-term research goal, this dissertation concentrates on the last phase of the mosaic creation pipeline - the composition of registered images into a seamless composite. The work detailed in this dissertation provides the technologies to fully realize interactive editing in mosaic composition on image collections ranging from the very small to massive in scale

Compression progressive de modèles de plantes à base de cylindres généralisés

National audienceCe papier présente nos travaux récents sur la compression progressive de modèles de plantes à base de cylindres généralisés. Cette représentation multi-resolution est compatible avec une représentation sous forme de graphe orienté sans cycle, ce qui nous permet de bénéficier des techniques de streaming progressif proposées dans cheng07analytical. Un codage différentiel des plantes est présenté: pour un groupe choisi de branches on calcule une branche moyenne, et pour chaque branche, il reste à coder une transformation et des différences. En vue du streaming, nous identifions et exploitons deux types de dépendances: topologiques (entre branche fille et mère) et dues au codage différentiel. Nous obtenons un modèle progressif qui permet la sélection d'une représentation plus légère de la plante, tout en gardant la même densité de branches

Performance Evaluation of Video Server Replication in Metro/Access Networks

Internet traffic is increasingly becoming a media-streaming traffic. Especially, Video-on-Demand (VoD) services are pushing the demand for broadband connectivity to the Internet, and optical fiber technology is being deployed in the access network to keep up with such increasing demand. To provide a more scalable network architecture for video delivery, network operators are currently considering novel metro/access network architectures which can accommodate replicated video servers directly in their infrastructure. When servers for VoD delivery are placed nearer to the end users, part of the traffic can be offloaded from the core segment of the network, and the end users can experience better Quality of Service (QoS). While the deployment of caching systems for traffic offloading has been studied in the core network, no work has already investigated the potential performance gains by replicating the content in the metro/access segment of the network, even closer to the users. In our work, we will compare the performance of video server replication in different metro/access network architectures, i.e. a metro ring architecture and a tree-based architecture, by considering both active and passive technologies. We will evaluate using both simulative and analytical methodologies how content providers could benefit from the deployment of replicas of video servers in terms of blocking probability of the VoD requests

Streaming of High-resolution Progressive Meshes Over The Internet

Ph.DDOCTOR OF PHILOSOPH