10 research outputs found

    An Information-Theoretic Framework for Consistency Maintenance in Distributed Interactive Applications

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    Distributed Interactive Applications (DIAs) enable geographically dispersed users to interact with each other in a virtual environment. A key factor to the success of a DIA is the maintenance of a consistent view of the shared virtual world for all the participants. However, maintaining consistent states in DIAs is difficult under real networks. State changes communicated by messages over such networks suffer latency leading to inconsistency across the application. Predictive Contract Mechanisms (PCMs) combat this problem through reducing the number of messages transmitted in return for perceptually tolerable inconsistency. This thesis examines the operation of PCMs using concepts and methods derived from information theory. This information theory perspective results in a novel information model of PCMs that quantifies and analyzes the efficiency of such methods in communicating the reduced state information, and a new adaptive multiple-model-based framework for improving consistency in DIAs. The first part of this thesis introduces information measurements of user behavior in DIAs and formalizes the information model for PCM operation. In presenting the information model, the statistical dependence in the entity state, which makes using extrapolation models to predict future user behavior possible, is evaluated. The efficiency of a PCM to exploit such predictability to reduce the amount of network resources required to maintain consistency is also investigated. It is demonstrated that from the information theory perspective, PCMs can be interpreted as a form of information reduction and compression. The second part of this thesis proposes an Information-Based Dynamic Extrapolation Model for dynamically selecting between extrapolation algorithms based on information evaluation and inferred network conditions. This model adapts PCM configurations to both user behavior and network conditions, and makes the most information-efficient use of the available network resources. In doing so, it improves PCM performance and consistency in DIAs

    Mobile three-dimensional city maps

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    Maps are visual representations of environments and the objects within, depicting their spatial relations. They are mainly used in navigation, where they act as external information sources, supporting observation and decision making processes. Map design, or the art-science of cartography, has led to simplification of the environment, where the naturally three-dimensional environment has been abstracted to a two-dimensional representation, populated with simple geometrical shapes and symbols. However, abstract representation requires a map reading ability. Modern technology has reached the level where maps can be expressed in digital form, having selectable, scalable, browsable and updatable content. Maps may no longer even be limited to two dimensions, nor to an abstract form. When a real world based virtual environment is created, a 3D map is born. Given a realistic representation, would the user no longer need to interpret the map, and be able to navigate in an inherently intuitive manner? To answer this question, one needs a mobile test platform. But can a 3D map, a resource hungry real virtual environment, exist on such resource limited devices? This dissertation approaches the technical challenges posed by mobile 3D maps in a constructive manner, identifying the problems, developing solutions and providing answers by creating a functional system. The case focuses on urban environments. First, optimization methods for rendering large, static 3D city models are researched and a solution provided by combining visibility culling, level-of-detail management and out-of-core rendering, suited for mobile 3D maps. Then, the potential of mobile networking is addressed, developing efficient and scalable methods for progressive content downloading and dynamic entity management. Finally, a 3D navigation interface is developed for mobile devices, and the research validated with measurements and field experiments. It is found that near realistic mobile 3D city maps can exist in current mobile phones, and the rendering rates are excellent in 3D hardware enabled devices. Such 3D maps can also be transferred and rendered on-the-fly sufficiently fast for navigation use over cellular networks. Real world entities such as pedestrians or public transportation can be tracked and presented in a scalable manner. Mobile 3D maps are useful for navigation, but their usability depends highly on interaction methods - the potentially intuitive representation does not imply, for example, faster navigation than with a professional 2D street map. In addition, the physical interface limits the usability

    Reducing the effect of network delay on tightly-coupled interaction

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    Tightly-coupled interaction is shared work in which each person’s actions immediately and continuously influence the actions of others. Tightly-coupled interaction is a hallmark of expert behaviour in face-to-face activity, but becomes extremely difficult to accomplish in distributed groupware. The main cause of this difficulty is network delay – even amounts as small as 100ms – that disrupts people’s ability to synchronize their actions with another person. To reduce the effects of delay on tightly-coupled interaction, I introduce a new technique called Feedback-Feedthrough Synchronization (FFS). FFS causes visual feedback from an action to occur at approximately the same time for both the local and the remote person, preventing one person from getting ahead of the other in the coordinated interaction. I tested the effects of FFS on group performance in several delay conditions, and my study showed that FFS substantially improved users’ performance: accuracy was significantly improved at all levels of delay, and without noticeable increase in perceived effort or frustration. Techniques like FFS that support the requirements of tightly-coupled interaction provide new means for improving the usability of groupware that operates on real-world networks

    A GPU-based architeture for supporting 3D interactions

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    Orientador: Wu Shin-TingTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de ComputaçãoResumo: Tendo como hipótese de que o controle preciso do movimento de um cursor constitui uma das técnicas elementares para as tarefas de manipulação direta 3D, esta tese propõe uma arquitetura de suporte a controles configuráveis dos movimentos de cursores em relação a modelos deformados em hardware gráfico. De forma integrada ao fluxo programável de visualização, a arquitetura calcula atributos de geometria diferencial discreta dos modelos processados, codificando tais atributos em pixels de buffers de renderização não visíveis. Mostramos, através de estudos de casos, que o uso desses atributos é suficiente para estabelecer uma correspondência entre o espaço discreto do modelo renderizado na tela e o espaço contínuo do modelo submetido ao fluxo de visualização. Isto permite que os cursores sejam posicionados de forma consistente com aquilo que o usuário está visualizando, proporcionando uma interação mais acurada. Testes de desempenho e robustez são conduzidos para validar a arquitetura. Uma biblioteca de funções que encapsula a arquitetura é apresentada, juntamente com exemplos de tarefas de manipulação direta 3D implementadas através delaAbstract: Based on the hypothesis that the precise control of the motion of a cursor constitutes one of the elementary techniques for 3D direct manipulation tools, this thesis proposes an architecture for supporting a configurable control of the motion of cursors with respect to models deformed on graphics hardware. Integrated with the actual programmable rendering pipeline, the architecture computes discrete differential geometric attributes of the processed models and encodes such attributes in pixels of off-screen render buffers. We show, through case studies, that these attributes are sufficient to establish a correspondence between the discrete space of the model rendered on the screen and the continuous space of the model submitted to the rendering pipeline. As a result, the cursors can be positioned consistently with what the user is actually viewing, thus providing a more accurate interaction. Efficiency and reliability tests are conducted to validate the architecture. A library of functions that encapsulates the architecture and examples of 3D direct manipulation tasks implemented with it are also presented.DoutoradoEngenharia de ComputaçãoDoutor em Engenharia Elétric

    Virtual Reality Games for Motor Rehabilitation

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    This paper presents a fuzzy logic based method to track user satisfaction without the need for devices to monitor users physiological conditions. User satisfaction is the key to any product’s acceptance; computer applications and video games provide a unique opportunity to provide a tailored environment for each user to better suit their needs. We have implemented a non-adaptive fuzzy logic model of emotion, based on the emotional component of the Fuzzy Logic Adaptive Model of Emotion (FLAME) proposed by El-Nasr, to estimate player emotion in UnrealTournament 2004. In this paper we describe the implementation of this system and present the results of one of several play tests. Our research contradicts the current literature that suggests physiological measurements are needed. We show that it is possible to use a software only method to estimate user emotion

    Animating jellyfish through numerical simulation and symmetry exploitation

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    This thesis presents an automatic animation system for jellyfish that is based on a physical simulation of the organism and its surrounding fluid. Our goal is to explore the unusual style of locomotion, namely jet propulsion, which is utilized by jellyfish. The organism achieves this propulsion by contracting its body, expelling water, and propelling itself forward. The organism then expands again to refill itself with water for a subsequent stroke. We endeavor to model the thrust achieved by the jellyfish, and also the evolution of the organism's geometric configuration. We restrict our discussion of locomotion to fully grown adult jellyfish, and we restrict our study of locomotion to the resonant gait, which is the organism's most active mode of locomotion, and is characterized by a regular contraction rate that is near one of the creature's resonant frequencies. We also consider only species that are axially symmetric, and thus are able to reduce the dimensionality of our model. We can approximate the full 3D geometry of a jellyfish by simulating a 2D slice of the organism. This model reduction yields plausible results at a lower computational cost. From the 2D simulation, we extrapolate to a full 3D model. To prevent our extrapolated model from being artificially smooth, we give the final shape more variation by adding noise to the 3D geometry. This noise is inspired by empirical data of real jellyfish, and also by work with continuous noise functions from the graphics community. Our 2D simulations are done numerically with ideas from the field of computational fluid dynamics. Specifically, we simulate the elastic volume of the jellyfish with a spring-mass system, and we simulate the surrounding fluid using the semi-Lagrangian method. To couple the particle-based elastic representation with the grid-based fluid representation, we use the immersed boundary method. We find this combination of methods to be a very efficient means of simulating the 2D slice with a minimal compromise in physical accuracy

    Augmented reality for non-rigid surfaces

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    Augmented Reality (AR) is the process of integrating virtual elements in reality, often by mixing computer graphics into a live video stream of a real scene. It requires registration of the target object with respect to the cameras. To this end, some approaches rely on dedicated hardware, such as magnetic trackers or infra-red cameras, but they are too expensive and cumbersome to reach a large public. Others are based on specifically designed markers which usually look like bar-codes. However, they alter the look of objects to be augmented, thereby hindering their use in application for which visual design matters. Recent advances in Computer Vision have made it possible to track and detect objects by relying on natural features. However, no such method is commonly used in the AR community, because the maturity of available packages is not sufficient yet. As far as deformable surfaces are concerned, the choice is even more limited, mainly because initialization is so difficult. Our main contribution is therefore a new AR framework that can properly augment deforming surfaces in real-time. Its target platform is a standard PC and a single webcam. It does not require any complex calibration procedure, making it perfectly suitable for novice end-users. To satisfy to the most demanding application designers, our framework does not require any scene engineering, renders virtual objects illuminated by real light, and let real elements occlude virtual ones. To meet this challenge, we developed several innovative techniques. Our approach to real-time registration of a deforming surface is based on wide-baseline feature matching. However, traditional outlier elimination techniques such as RANSAC are unable to handle the non-rigid surface's large number of degrees of freedom. We therefore proposed a new robust estimation scheme that allows both 2–D and 3–D non-rigid surface registration. Another issue of critical importance in AR to achieve realism is illumination handling, for which existing techniques often require setup procedures or devices such as reflective spheres. By contrast, our framework includes methods to estimate illumination for rendering purposes without sacrificing ease of use. Finally, several existing approaches to handling occlusions in AR rely on multiple cameras or can only deal with occluding objects modeled beforehand. Our requires only one camera and models occluding objects at runtime. We incorporated these components in a consistent and flexible framework. We used it to augment many different objects such as a deforming T-shirt or a sheet of paper, under challenging conditions, in real-time, and with correct handling of illumination and occlusions. We also used our non-rigid surface registration technique to measure the shape of deformed sails. We validated the ease of deployment of our framework by distributing a software package and letting an artist use it to create two AR applications

    Un modèle d'environnement pour la simulation multiniveau - Application à la simulation de foules

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    Cette thèse propose un modèle organisationnel et holonique de l'environnement pour la simulation des déplacements de piétons dans des bâtiments. Une foule de piétons peut être considérée comme un système composé d'un grand nombre d'entités en interaction, dont la dynamique globale ne peut se réduire à la somme des comportements de ses composants. La simulation multiniveau fondée sur les modèles multiagents holoniques constitue une approche permettant d'analyser la dynamique de tels systèmes. Elle autorise leur analyse en considérant plusieurs niveaux d'observation (microscopique, mésoscopique et macroscopique) et prend en compte les ressources de calcul disponibles. Dans ces systèmes, l'environnement est considéré comme l'une des parties essentielles. La dynamique des piétons composant la foule est alors clairement distinguée de celle de l'environnement dans lequel ils se déplacent. Un modèle organisationnel décrivant la structure et la dynamique de l'environnement est proposé. L'environnement est structurellement décomposé en zones, sous-zones, etc. Les organisations et les rôles de cet environnement sont projetés dans une société d'agents ayant en charge de simuler la dynamique de l'environnement et les différentes missions qui lui sont classiquement assignées dans les systèmes multiagents. Ce modèle précise également les règles de passage entre deux niveaux d'observation. Ainsi, chaque agent appartenant au modèle de l'environnement tente d'utiliser une approximation des comportements de ses sous-zones afin de limiter la consommation de ressources durant la simulation. La qualité de l'approximation entre ces deux niveaux d'observation est évaluée avec des indicateurs énergétiques. Ils permettent de déterminer si l'agent approxime correctement les comportements des agents associés aux sous-zones. En sus du modèle organisationnel et holonique proposé, nous présentons un modèle concret de la simulation de voyageurs dans un terminal d'aéroport. Ce modèle concret est implanté sur les plateformes JaSIM et Janus.This work presents a holonic organizational model of the environment for the simulation of pedestrians in buildings. A crowd of pedestrians is considered as a system composed of a large number of interacting entities. The global dynamics of this system cannot be reduced to the sum of the behaviors of its components, Multilevel simulation based on holonic multiagent models is one approach to analyze the dynamics of such systems. It allows their analysis by considering several levels of observation (microscopic, mesoscopic and macroscopic) and the available computing resources. In these systems, the environment is considered as an essential part. The behavior of the crowd is clearly distinguished from the behavior of the environment in which the pedestrians move. An organizational model is proposed to describe the structure and the dynamics of the indoor environment. This environment is structurally divided into areas, sub-areas, etc. Organizations and roles are mapped into a society of agents in charge of simulating the dynamics of the environment and their various missions in multiagent systems. This model also specifies the rules for changing the level of observation dynamically. Thus, each agent belonging to the model of the environment tries to use an approximation of behaviors of its sub-zones, and at the same time to minimize the resource consumption. The quality of the approximation between these two levels is evaluated with energy-based indicators. They help to determine if the agent approximates the behaviors of its sub-agents correctly. In addition to the organizational and holonic model proposed in this work, we present a concrete model of the simulation of passengers in an airport terminal. This concrete model is implemented on the platforms JaSIM and Janus.BELFORT-UTBM-SEVENANS (900942101) / SudocSudocFranceF

    MaxControl: ein objektorientiertes Werkzeug zur automatischen Erstellung von 3D-Computeranimationsfilmen und dessen Integration in eine professionelle 3D-Animationssoftware

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    Durch die wachsende Computerleistung können 3D-Computeranimationen sehr komplexe Szenen mit ebenso komplexen zeitlichen Abläufen animiert darstellen. Jedoch ist neben der Erstellung einer komplexen Szene auch deren Animation entsprechend aufwendig, wenn keine Automatisierungen genutzt werden können. Das in dieser Arbeit entwickelte Werkzeug MaxControl ist ein System zur automatischen Animation von nicht-interaktiven 3D-Animationsfilmen. Dies wird durch die Simulation von Verhaltensweisen erreicht, die den 3D-Objekten zugewiesen werden

    Safety and Reliability - Safe Societies in a Changing World

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    The contributions cover a wide range of methodologies and application areas for safety and reliability that contribute to safe societies in a changing world. These methodologies and applications include: - foundations of risk and reliability assessment and management - mathematical methods in reliability and safety - risk assessment - risk management - system reliability - uncertainty analysis - digitalization and big data - prognostics and system health management - occupational safety - accident and incident modeling - maintenance modeling and applications - simulation for safety and reliability analysis - dynamic risk and barrier management - organizational factors and safety culture - human factors and human reliability - resilience engineering - structural reliability - natural hazards - security - economic analysis in risk managemen
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