1,632 research outputs found
Constrained set-up of the tGAP structure for progressive vector data transfer
A promising approach to submit a vector map from a server to a mobile client is to send a coarse representation first, which then is incrementally refined. We consider the problem of defining a sequence of such increments for areas of different land-cover classes in a planar partition. In order to submit well-generalised datasets, we propose a method of two stages: First, we create a generalised representation from a detailed dataset, using an optimisation approach that satisfies certain cartographic constraints. Second, we define a sequence of basic merge and simplification operations that transforms the most detailed dataset gradually into the generalised dataset. The obtained sequence of gradual transformations is stored without geometrical redundancy in a structure that builds up on the previously developed tGAP (topological Generalised Area Partitioning) structure. This structure and the algorithm for intermediate levels of detail (LoD) have been implemented in an object-relational database and tested for land-cover data from the official German topographic dataset ATKIS at scale 1:50 000 to the target scale 1:250 000. Results of these tests allow us to conclude that the data at lowest LoD and at intermediate LoDs is well generalised. Applying specialised heuristics the applied optimisation method copes with large datasets; the tGAP structure allows users to efficiently query and retrieve a dataset at a specified LoD. Data are sent progressively from the server to the client: First a coarse representation is sent, which is refined until the requested LoD is reached
Streaming of High-resolution Progressive Meshes Over The Internet
Ph.DDOCTOR OF PHILOSOPH
Mesmerizer: A Effective Tool for a Complete Peer-to-Peer Software Development Life-cycle
In this paper we present what are, in our experience, the best
practices in Peer-To-Peer(P2P) application development and
how we combined them in a middleware platform called Mesmerizer. We explain how simulation is an integral part of
the development process and not just an assessment tool.
We then present our component-based event-driven framework for P2P application development, which can be used
to execute multiple instances of the same application in a
strictly controlled manner over an emulated network layer
for simulation/testing, or a single application in a concurrent
environment for deployment purpose. We highlight modeling aspects that are of critical importance for designing and
testing P2P applications, e.g. the emulation of Network Address Translation and bandwidth dynamics. We show how
our simulator scales when emulating low-level bandwidth
characteristics of thousands of concurrent peers while preserving a good degree of accuracy compared to a packet-level
simulator
Management of spatial data for visualization on mobile devices
Vector-based mapping is emerging as a preferred format in Location-based
Services(LBS), because it can deliver an up-to-date and interactive map visualization.
The Progressive Transmission(PT) technique has been developed to
enable the ecient transmission of vector data over the internet by delivering
various incremental levels of detail(LoD). However, it is still challenging to apply
this technique in a mobile context due to many inherent limitations of mobile
devices, such as small screen size, slow processors and limited memory. Taking
account of these limitations, PT has been extended by developing a framework of
ecient data management for the visualization of spatial data on mobile devices.
A data generalization framework is proposed and implemented in a software
application. This application can signicantly reduce the volume of data for
transmission and enable quick access to a simplied version of data while preserving
appropriate visualization quality. Using volunteered geographic information
as a case-study, the framework shows
exibility in delivering up-to-date spatial
information from dynamic data sources.
Three models of PT are designed and implemented to transmit the additional
LoD renements: a full scale PT as an inverse of generalisation, a viewdependent
PT, and a heuristic optimised view-dependent PT. These models are
evaluated with user trials and application examples. The heuristic optimised
view-dependent PT has shown a signicant enhancement over the traditional PT
in terms of bandwidth-saving and smoothness of transitions.
A parallel data management strategy associated with three corresponding
algorithms has been developed to handle LoD spatial data on mobile clients.
This strategy enables the map rendering to be performed in parallel with a process
which retrieves the data for the next map location the user will require. A viewdependent
approach has been integrated to monitor the volume of each LoD for
visible area. The demonstration of a
exible rendering style shows its potential
use in visualizing dynamic geoprocessed data. Future work may extend this
to integrate topological constraints and semantic constraints for enhancing the
vector map visualization
Dynamic Images Carousel Transmissions Over Multiple Multicast Groups
Pertumbuhan Internet yang medadak serta kemajuan yang pesat dalam teknologi komputer-meja tahap tinggi telah memudahkan penyebaran data dan multimedia pada skala yang lebih meluas.
The skyrocketing growth of internet and the advancement of high-end desktop computers have facilitated multimedia data distribution in large-scale
Dynamic Images Carousel Transmissions Over Multiple Multicast Groups [TK5105.2. S959 2004 f rb] [Microfiche 7962].
Pertumbuhan Internet yang medadak serta kemajuan yang pesat dalam teknologi komputer-meja tahap tinggi telah memudahkan penyebaran data dan multimedia pada skala yang lebih meluas.
The skyrocketing growth of internet and the advancement of high-end desktop computers have facilitated multimedia data distribution in large-scale
Web Application Performance Testing
Web application performance testing is an emerging and important field of software engineering. As web applications become more commonplace and complex, the need for performance testing will only increase.
This paper discusses common concepts, practices and tools that lie at the heart of web application performance testing. A pragmatic, hands-on approach is assumed where applicable; real-life examples of test tooling, execution and analysis are presented right next to the underpinning theory.
At the client-side, web application performance is primarily driven by the amount of data transmitted over the wire. At the server-side, selection of programming language and platform, implementation complexity and configuration are the primary contributors to web application performance.
Web application performance testing is an activity that requires delicate coordination between project stakeholders, developers, system administrators and testers in order to produce reliable and useful results. Proper test definition, execution, reporting and repeatable test results are of utmost importance.
Open-source performance analysis tools such as Apache JMeter, Firebug and YSlow can be used to realise effective web application performance tests. A sample case study using these tools is presented in this paper. The sample application was found to perform poorly even under the moderate load incurred by the sample tests.Siirretty Doriast
Transmission adaptative de modèles 3D massifs
Avec les progrès de l'édition de modèles 3D et des techniques de reconstruction 3D, de plus en plus de modèles 3D sont disponibles et leur qualité augmente. De plus, le support de la visualisation 3D sur le web s'est standardisé ces dernières années. Un défi majeur est donc de transmettre des modèles massifs à distance et de permettre aux utilisateurs de visualiser et de naviguer dans ces environnements virtuels. Cette thèse porte sur la transmission et l'interaction de contenus 3D et propose trois contributions majeures. Tout d'abord, nous développons une interface de navigation dans une scène 3D avec des signets -- de petits objets virtuels ajoutés à la scène sur lesquels l'utilisateur peut cliquer pour atteindre facilement un emplacement recommandé. Nous décrivons une étude d'utilisateurs où les participants naviguent dans des scènes 3D avec ou sans signets. Nous montrons que les utilisateurs naviguent (et accomplissent une tâche donnée) plus rapidement en utilisant des signets. Cependant, cette navigation plus rapide a un inconvénient sur les performances de la transmission : un utilisateur qui se déplace plus rapidement dans une scène a besoin de capacités de transmission plus élevées afin de bénéficier de la même qualité de service. Cet inconvénient peut être atténué par le fait que les positions des signets sont connues à l'avance : en ordonnant les faces du modèle 3D en fonction de leur visibilité depuis un signet, on optimise la transmission et donc, on diminue la latence lorsque les utilisateurs cliquent sur les signets. Deuxièmement, nous proposons une adaptation du standard de transmission DASH (Dynamic Adaptive Streaming over HTTP), très utilisé en vidéo, à la transmission de maillages texturés 3D. Pour ce faire, nous divisons la scène en un arbre k-d où chaque cellule correspond à un adaptation set DASH. Chaque cellule est en outre divisée en segments DASH d'un nombre fixe de faces, regroupant des faces de surfaces comparables. Chaque texture est indexée dans son propre adaptation set à différentes résolutions. Toutes les métadonnées (les cellules de l'arbre k-d, les résolutions des textures, etc.) sont référencées dans un fichier XML utilisé par DASH pour indexer le contenu: le MPD (Media Presentation Description). Ainsi, notre framework hérite de la scalabilité offerte par DASH. Nous proposons ensuite des algorithmes capables d'évaluer l'utilité de chaque segment de données en fonction du point de vue du client, et des politiques de transmission qui décident des segments à télécharger. Enfin, nous étudions la mise en place de la transmission et de la navigation 3D sur les appareils mobiles. Nous intégrons des signets dans notre version 3D de DASH et proposons une version améliorée de notre client DASH qui bénéficie des signets. Une étude sur les utilisateurs montre qu'avec notre politique de chargement adaptée aux signets, les signets sont plus susceptibles d'être cliqués, ce qui améliore à la fois la qualité de service et la qualité d'expérience des utilisateur
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