Higher level techniques for the artistic rendering of images and video

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Designable Visual Markers for Mobile Human-Computer Interaction

Visual markers are graphic symbols designed to be easily recognised by machines. They are traditionally used to track goods, but there is increasing interest in their application to mobile human-computer interaction (HCI). By scanning a visual marker through a camera phone, users can retrieve localised information and access mobile services. In particular the dissertation examines the application of visual markers to physical tagging: practices of association of digital information with physical items. One missed opportunity in current visual marker systems is that the markers themselves cannot be visually designed; they are not expressive to humans, and thus fail to convey information before being scanned. To address this limitation, this dissertation introduces the idea of designable markers, visual markers that are both machine-readable and visually communicative to humans, and presents an investigation of the ways in which they can support mobile human-computer interaction. The application of designable visual markers to the creation of mobile interfaces is explored through a variety of methods: through formal usability experiments, through the creation and analysis of example designs, as well as through the qualitative analysis of two field trials. All three approaches were enabled by the engineering and development of d-touch, an actual recognition system that supports designable visual markers and by its integration in a variety of applications and experimental probes. D-touch is based on image topology, and its markers are defined in terms of constraints on the nesting of dark and light regions. The constraints imposed by d-touch are flexible enough to allow novice users to create markers which are visually expressive and at the same time machine readable. A user study demonstrates how such system enables people to design their own functional visual markers, determining their aesthetic qualities and what they visually communicate to others. A desktop application to support users in the creation of valid markers, the d-touch analyser, is presented and its usefulness is demonstrated through the same study. A formal usability experiment comparing five variations of marker-based interfaces on keypad and touch-screen phones shows that all of them allow users to reliably select targets within, on average, less than 4 seconds. Participants of the experiment reported a strong preference for interfaces that involve only marker scanning, compared to those that require a combination of marker scanning and key-presses or touch selections. Example designs of mobile interface generated by the author as well as others are presented to expose how the d-touch recognition system can be integrated in mobile applications. The examples illustrate a variety of ways in which markers can be used to augment printed materials such as cards, books and product packages, adding to them interactive capabilities. The examples show also different approaches to marker design, ranging from simple and recognisable iconic design, to symbols that integrate cues about the interactive functionality, to making them invisible by hiding them in existing graphics. Finally, the dissertation reports and analyses two field trials conducted to study what practices of physical tagging can emerge from, and be supported by, the use of markers. The trials were centred around the use of uWiki, a functional prototype based on d-touch, that allows users to associate digital content to markers printed on physical tags that can be affixed to objects or buildings. Observations show that a variety of practices emerge around the use of this technology, indicating that they provide a rich medium that has potential to attract the interest of real users. Though the results of this work are preliminary, they serve to demonstrate the range of potential for the future of such systems

Human-Centric Machine Vision

Recently, the algorithms for the processing of the visual information have greatly evolved, providing efficient and effective solutions to cope with the variability and the complexity of real-world environments. These achievements yield to the development of Machine Vision systems that overcome the typical industrial applications, where the environments are controlled and the tasks are very specific, towards the use of innovative solutions to face with everyday needs of people. The Human-Centric Machine Vision can help to solve the problems raised by the needs of our society, e.g. security and safety, health care, medical imaging, and human machine interface. In such applications it is necessary to handle changing, unpredictable and complex situations, and to take care of the presence of humans

Methods for transform, analysis and rendering of complete light representations

Recent advances in digital holography, optical engineering and computer graphics have opened up the possibility of full parallax, three dimensional displays. The premises of these rendering systems are however somewhat different from traditional imaging and video systems. Instead of rendering an image of the scene, the complete light distribution must be computed. In this thesis we discuss some different methods regarding processing and rendering of two well known full light representations: the light field and the hologram. A light field transform approach, based on matrix optics operators, is introduced. Thereafter we discuss the relationship between the light field and the hologram representations. The final part of the thesis is concerned with hologram and wave field synthesis. We present two different methods. First, a GPU accelerated approach to rendering point-based models is introduced. Thereafter, we develop a Fourier rendering approach capable of generating angular spectra of triangular mesh models.Aktuelle Fortschritte in den Bereichen der digitalen Holographie, optischen Technik und Computergrafik ermöglichen die Entwicklung von vollwertigen 3D-Displays. Diese Systeme sind allerdings auf Eingangsdaten angewiesen, die sich von denen traditioneller Videosysteme unterscheiden. Anstatt für die Visualisierung ein zweidimensionales Abbild einer Szene zu erstellen, muss die vollständige Verteilung des Lichts berechnet werden. In dieser Dissertation betrachten wir verschiedene Methoden, um dies für zwei verschiedene gebräuchliche Darstellungen der Lichtverteilung zu erreichen: Lichtfeld und Hologramm. Wir stellen dafür zunächst eine Methode vor, die Operatoren der Strahlenoptik auf Lichtfelder anzuwenden, und diskutieren daraufhin, wie die Darstellung als Lichtfeld mit der Darstellung als Hologramm zusammenhängt. Abschliessend wird die praktische Berechnung von Hologrammen und Wellenfeldern behandelt, wobei wir zwei verschiedene Ansätze untersuchen. Im ersten Ansatz werden Wellenfelder aus punktbasierten Modellen von Objekten erzeugt, unter Einsatz moderner Grafikhardware zur Optimierung der Rechenzeit. Der zweite Ansatz, Fourier-Rendering, ermöglicht die Generierung von Hologrammen aus Oberflächen, die durch Dreiecksnetze beschrieben sind

Méthodes de rendu à base de vidéos et applications à la réalité Virtuelle

Given a set images of the same scene, the goal of video-based rendering methods is to compute new views of this scene from new viewpoints. The user of this system controls the virtual camera's movement through the scene. Nevertheless, the virtual images are computed from static cameras. A first approach is based on a reconstruction of the scene and can provide accurate models but often requires lengthy computation before visualization. Other methods try to achieve real-time rendering. Our main contribution to video-base rendering concerns the plane sweep method which belongs to the latter family. The plane sweep method divides space in parallel planes. Each point of each plane is processed independently in order to know if it lies on the surface of an object of the scene. These informations are used to compute a new view of the scene from a new viewpoint. This method is well suited to an implementation using graphic hardware and thus to reach realtime rendering. Our main contribution to this method concerns the way to consider whether a point of a plane lies on the surface of an object of the scene. We first propose a new scoring method increasing the visual quality of the new images. Compared with previous approaches, this method implies fewer constraints on the position of the virtaul camera, i.e. this camera does not need to lie between the input camera's area. We also present an adaptation of the plane sweep algorithm that handles partial occlusions. According to video-based rendering practical applications in virtual reality, we propose an improvement of the plane sweep method dealing with stereoscopic images computation that provides visualization of the virtual scene in relief. Our enhancement provides the second view with only low additional computation time whereas most of the others techniques require to render the scene twice. This improvement is based on a sharing of the informations common to the two stereoscopic views. Finally, we propose a method that removes pseudoscopic movements in a virtual reality application. These pseudoscopic movements appear when the observer moves in front of the stereoscopic screen. Then the scene roportions seem to be distorted and the observer sees the objects of the scene moving in an anormal way. The method we propose is available either on a classical stereoscopic rendering method or on the Plane Seep algorithm. Every method we propose widely uses graphic harware through to shader programs and provides real-time rendering. These methods only require a standard computer, a video acquisition device and a powerful enough graphic card. There exists a lot of practicalapplications of the plane sweep method, especially in fields like virtual reality, video games, 3d television or security.Etant donné un ensemble de caméras filmant une même scène, le rendu à base de vidéos consiste à générer de nouvelles images de cette scène à partir de nouveaux points de vue. L'utilisateur a ainsi l'impression de pouvoir déplacer une caméra virtuelle dans la scène alors qu'en réalité, toutes les caméras sont fixes. Certaines méthodes de rendu à base de vidéos coûteuses en temps de calcul se basent sur une reconstruction 3d de la scène et produisent des images de très bonne qualité. D'autres méthodes s'orientent plutôt vers le rendu temps réel. C'est dans cette dernière catégorie que s'inscrit la méthode de Plane Sweep sur laquelle porte la majeure partie de nos travaux. Le principe de la méthode des Plane Sweep consiste à discrétiser la scène en plans parallèles et à traiter séparément chaque point de ces plans afin de déterminer s'ils se trouvent ou non sur la surface d'un objet de la scène. Les résultats obtenus permettent de générer une nouvelle image de la scène à partir d'un nouveau point de vue. Cette méthode est particulièrement bien adaptée à une utilisation optimale des ressources de la carte graphique ce qui explique qu'elle permette d'effectuer du rendu en temps réel. Notre principale contribution à cette méthode concerne la façon d'estimer si un point d'un plan représente la surface d'un objet. Nous proposons d'une part un nouveau mode de calcul permettant d'améliorer le résultat visuel tout en rendant la navigation de la caméra virtuelle plus souple. D'autre part, nous présentons une adaptation de la méthode des Plane Sweep permettant de gérer les occlusions partielles. Compte tenu des applications du rendu à base de vidéos en réalité virtuelle, nous proposons une amélioration des Plane Sweep appliquée à la réalité virtuelle avec notamment la création de paires d'images stéréoscopiques permettant de visualiser en relief la scène reconstruite. Notre amélioration consiste à calculer la seconde vue à moindre coût alors qu'une majorité des méthodes concurrentes sont contraintes d'effectuer deux rendus indépendants. Cette amélioration est basée sur un partage des données communes aux deux vues stéréoscopiques. Enfin, dans le cadre de l'utilisation des Plane Sweep en réalité virtuelle, nous présentons une méthode permettant de supprimer les mouvements pseudoscopiques. Ces mouvements pseudoscopiques apparaissent lorsque l'observateur se déplace devant une image stéréoscopique, il ressent alors une distorsion des proportions de la scène virtuelle et voit les objets se déplacer de façon anormale. La méthode de correction que nous proposons est applicable d'une part à des méthodes classiques de rendu d'images de synthèse et d'autre part à la méthode des Plane Sweep. Toutes les méthodes que nous présentons utilisent largement les possibilités du processeur de la carte graphique à l'aide des shader programs et génèrent toutes des images en temps réel. Seuls un ordinateur grand public, un dispositif d'acquisition vidéo et une bonne carte graphique sont suffisants pour les faire fonctionner. Les applications des Plane Sweep sont nombreuses, en particulier dans les domaines de la réalité virtuelle, du jeu vidéo, de la télévision 3d ou de la sécurité

Semantic models for texturing volume objects

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Courtroom Discourses: An Analysis of the Westerfield Jury Trial

Alla luce del crescente interesse verso le complesse dinamiche che uniscono inestricabilmente i concetti di legge e linguaggio, questo lavoro mira ad osservare tali dinamiche in un particolare evento comunicativo, ovvero un processo con giuria popolare. Pi\uf9 specificatamente, viene analizzato il caso California vs Westerfield, svoltosi in California nel 2002. Lo studio si basa in particolare sull\u2019osservazione dei processi comunicativi che avvengono tra professionisti del mondo legale (in particolare giudice ed avvocati) e i giurati, che per definizione non possiedono una specifica conoscenza in ambito giuridico. La relazione tra esperti e non-esperti in un processo \ue8 inoltre determinata dalla peculiarit\ue0 che da un lato i professionisti detengono una posizione vantaggiosa in termini di potere comunicativo e di conoscenze specifiche, ma al contempo il potere decisionale \ue8 ascritto esclusivamente ai giurati. Lo scopo primario \ue8 quello di giungere ad una migliore comprensione della complessa natura delle tecniche e delle strategie discorsive che emergono nella relazione tra professionisti e non in questo specifico evento. Dal punto di vista delle dinamiche comunicative i giurati sembrano assumere un ruolo di passivi spettatori dell\u2019evento che viene loro presentato e la relazione tra diversi partecipanti \ue8 caratterizzata da un\u2019asimmetrica distribuzione dei turni e delle possibilit\ue0 di intervento. Tale relazione \ue8 determinata da specifiche pratiche e restrizioni procedurali di un evento che \ue8 per definizione altamente istituzionalizzato. Al contempo per\uf2 l\u2019analisi prende in considerazione le molteplici sfumature che definiscono queste dinamiche e le varie possibilit\ue0 che i giurati possiedono per intervenire in modo pi\uf9 attivo nel processo, in particolare alla luce dei recenti sviluppi procedurali. Il lavoro osserva l\u2019ibridit\ue0 del linguaggio usato in tribunale, adottando diverse prospettive. Innanzitutto si studia la complessa relazione che esiste tra la modalit\ue0 scritta e quella orale durante diverse fasi del processo. L\u2019ibridit\ue0 \ue8 anche analizzata dal punto di vista della commistione di diversi stili e registri. Inoltre, lo studio osserva se e in che modo le caratteristiche che vengono generalmente attribuite al linguaggio legale, quali la presenza di lessico altamente specializzato, di strutture sintattiche complesse e di un registro molto formale, emergono in questo specifico tipo di processo. Particolare attenzione \ue8 dedicata all\u2019osservazione delle modalit\ue0 attraverso le quali specifici concetti giuridici vengono illustrati ai giurati in base ai diversi scopi comunicativi. Diversi tipi di tensioni vengono osservati all\u2019interno di questo contesto, quali la giustapposizione di tecnicismi e colloquialismi, o il conflitto tra il desiderio di sensazionalismo e la necessit\ue0 di muoversi all\u2019interno di un quadro standardizzato e caratterizzato da specifici vincoli procedurali.Given the increasing interest in the complex dynamics that inextricably combine the concepts of law and language, this work aims to examine these dynamics focusing on a particular communicative event, namely a trial by jury. More specifically, the case under scrutiny is California vs Westerfield, which was tried in California in 2002. The study is based on the observation of the communicative processes taking place between professionals (specifically, judges and lawyers) and jurors, who by definition do not possess any specific legal knowledge. The relationship between experts and non-experts in a trial is also determined by the peculiarity that professionals assumes an advantageous position in terms of communicative power and specialized knowledge, while the decisional power is ascribed exclusively to the jury. The primary goal of this work is to reach a better understanding of the complex nature of the techniques and discursive strategies that emerge in the communicative relationship between professionals and laymen in this particular event. From a communicative perspective, the jurors seem to assume the role of passive spectators, and the relationship between different participants is characterized by an asymmetric distribution of turns and limited active intervention. These dynamics are determined by the specific practices and procedural restrictions of an event that is by definition highly institutionalized. At the same time, however, the analysis takes into account the many nuances that define these dynamics and the various possibilities that the jurors have to intervene more actively in the process, particularly in the light of recent procedural developments. The work aims to observe the hybridity of the language used in court, adopting different perspectives. First, it investigates the complex relationship that emerges between written and oral communication in different phases of the trial. Hybridity is also observed from the point of view of the combination of different styles and registers. The study also examines to what extent the characteristics that are generally attributed to legal language, such as the presence of highly specialized vocabulary, complex syntactic structures and a very formal register emerge in this specific context. Particular attention is devoted to the observation of the specific strategies adopted to illustrate legal ideas and concepts to the jurors in light of the speaker\u2019s various communicative purposes. Several kinds of tensions are observed within this context, such as the juxtaposition of colloquialisms and jargon, and the conflict between the desire for sensationalism and the need to move within a standardized framework that is characterized by specific procedural constraints