Depuis plusieurs années, on cherche à fonctionnaliser les surfaces de tout type de matériaux que ce soit pour le biomédical, la recherche ou l’industrie des transports afin de conférer de nouvelles propriétés (antibuée, réduction du frottement, dégivrage…). Parmi les techniques de traitement de surface, l’ablation au moyen d’un laser à impulsions ultra-brèves offre la possibilité d’élaborer des textures submicroniques, qui jouent un rôle essentiel dans leur comportement fonctionnel. Toutefois, dans le cas de production en grande série, il est préférable pour des questions de coûts, de reproduire ces textures avec une technique de reproduction d’empreinte.Ce travail porte sur l’étude des différents facteurs impliqués dans la réplication par injection plastique de topographies submicroniques. Il s’agit de comprendre l’influence des paramètres du procédé d’injection, des propriétés du polymère injecté et de la chimie de surface du moule (avec ou sans revêtement) sur la qualité de la pièce injectée.Une première étude a été réalisée sur deux polypropylènes de viscosité différente sous faible taux de cisaillement (grade MFR). Une première étape a consisté à développer une nouvelle méthodologie pour quantifier la qualité de réplication de structures submicroniques périodiques et aléatoires entre la pièce injectée et le moule, avant de mettre en œuvre une série d’injections. Pour des paramètres d’injection identiques, on observe que la qualité de réplication des motifs sur les pièces injectées est différente. Une étude approfondie des caractéristiques structurales et rhéologiques des polymères a été réalisée. Cette différence de réplication n’est pas dues à leur viscosité dans les conditions d’injection en dépit de grades MFR très différents mais de leur mode de relaxation de contraintes pendant la phase de refroidissement [1]. Une deuxième étude s’est concentrée sur l’influence de la chimie de surface des moules lors du remplissage des cavités dans le procédé d’injection. Nous avons principalement étudié le phénomène d’adhésion d’un polymère fondu sur différents substrats revêtus de dépôt à base de nitrures de chrome ou de titane ainsi qu’un dépôt de DLC (Diamond Like Carbon). A partir d’essais de mouillage en température et de mesures d’énergie de surface des polymères fondus, nous avons déterminé le travail d’adhésion du polymères sur les moules revêtus (ou non) aux températures d’injection [2]. A partir de ces résultats nous avons tenté de mener un travail de synthèse en développant une approche statistique basée sur l’analyse de plans d’expériences afin de quantifier l’influence de différents facteurs tant procédés (vitesses d’injection, vide dans l’empreinte, température moule, …) que matériaux (différents polymères, différents revêtements sur le moule). Nous avons montré que les échanges thermiques à l’interface moule-polymère avaient un rôle prépondérant dans la qualité de réplication. Ces échanges dépendent notamment de la nature des revêtements qui conditionne la formation de la gaine solide lors de la microinjection [3].[1] J. Vera, A.-C. Brulez, E. Contraires, M. Larochette, S. Valette, S. Benayoun, Influence of the polypropylene structure on the replication of nanostructures by injection molding, J. Micromech. Microeng. 25 (2015) 115027. doi:10.1088/0960-1317/25/11/115027.[2] J. Vera, E. Contraires, A.-C. Brulez, M. Larochette, S. Valette, S. Benayoun, Wetting of polymer melts on coated and uncoated steel surfaces, Applied Surface Science. 410 (2017) 87–98. doi:10.1016/j.apsusc.2017.02.067.[3] J. Vera, A.-C. Brulez, E. Contraires, M. Larochette, N. Trannoy-Orban, M. Pignon, C. Mauclair, S. Valette, S. Benayoun, Factors influencing micro-injection quality, Journal of Micromechanics and Microengineering. (soumis en juin 2017). / Over the past decades, industrial and academic research groups have been trying to functionalize surfaces, i.e. provide new properties to surfaces, in order to obtain specific functions such as friction reduction, anti-fog or de-icing properties. Among the various existing surface treatment techniques, laser ablation using an ultra-short pulse laser gives the opportunity to generate submicronic textures, which play an essential role in their functional behavior. However, in the case of mass production of textured surfaces, it is preferable to reproduce these textures with a fingerprinting technique for reasons of cost-effectiveness.This work focuses on the study of the various factors involved in the replication of submicronic topographies by plastic injection. Understanding the influence of the parameters of the injection process, the properties of the injected polymer and the surface chemistry of the mold (with or without coating) is key to controlling the quality of the injected part.A first study was carried out on two polypropylenes of different viscosities under low shear rate (MFR grade). A first step was to develop a methodology enabling to quantify the quality of replication of periodic and random submicron structures between the injected part and the mold. For identical injection parameters, it was observed that the quality of replication of the patterns on the injected parts was different when viscosity changed. A study of the structural and rheological characteristics of the polymers was carried out. This difference in replication was not due to their viscosity under the injection conditions in spite of very different MFR grades but to their mode of stress relaxation during the cooling phase [1]. A second study focused on the influence of the surface chemistry of molds when filling the cavities in the injection process. We mainly studied the phenomenon of adhesion of a molten polymer on different chromium nitride, titanium-based and DLC films deposited on mold substrates. From the temperature wetting tests and the surface energy measurements of the molten polymers, we determined the work of adhesion between the polymers and the coated or non-coated molds at injection temperatures [2]. On the basis of these results, we performed a synthesis work by developing a statistical approach based on the analysis of experimental plans in order to quantify the influence of various factors, both process (injection rates, Impression, mold temperature, etc.) and material (different polymers, different coatings on the mold) related. We showed that thermal exchanges at the mold-polymer interface had a dominant role in the quality of replication. In particular, these exchanges depend on the nature of the coatings and regulates the formation of the solid sheath during microinjection [3].[1] J. Vera, A.-C. Brulez, E. Contraires, M. Larochette, S. Valette, S. Benayoun, Influence of the polypropylene structure on the replication of nanostructures by injection molding, J. Micromech. Microeng. 25 (2015) 115027. doi:10.1088/0960-1317/25/11/115027.[2] J. Vera, E. Contraires, A.-C. Brulez, M. Larochette, S. Valette, S. Benayoun, Wetting of polymer melts on coated and uncoated steel surfaces, Applied Surface Science. 410 (2017) 87–98. doi:10.1016/j.apsusc.2017.02.067.[3] J. Vera, A.-C. Brulez, E. Contraires, M. Larochette, N. Trannoy-Orban, M. Pignon, C. Mauclair, S. Valette, S. Benayoun, Factors influencing micro-injection quality, Journal of Micromechanics and Microengineering. (soumis en juin 2017).

Le travail présenté dans cette thèse s’inscrit dans le domaine de l’analyse d’images texturées 3D aussi connu sous le nom de textures solides ou textures volumétriques. Partant de l’hypothèse qu’il est plus pertinent de décrire une texture avec des adjectifs qualificatifs plutôt qu’avec un modèle mathématique unique, nous avons choisi de définir un nouvel ensemble de descripteurs de textures permettant une caractérisation qualitative des textures contenues dans les images 3D. Ces nouveaux attributs permettent entre autres de décrire des propriétés texturales telles que la directionnalité, la rugosité, le contraste, la régularité ainsi que des informations de forme. Afin de les calculer, nous proposons un système multirésolution basé sur une décomposition en ondelette couplée à une analyse des composantes géométriques contenues dans les représentations obtenues. Ces caractéristiques sont exploitées par un logiciel, proposant une interface Homme-Machine interactive, afin de segmenter des images échographiques 3D. / This work deals with the domain of 3D textured images also known as solid textures or volumetric textures. Supposing that it is more relevant to describe a texture using qualifier adjectives than using a single mathematic model, we choose to define a new set of texture descriptors that allows us to have a qualitative characterisation of 3D images. These new attributes can quantify textural properties such as the directionality, the roughness, the contrast, the regularity but also information on shapes. To compute them, we propose a multiresolution system which associate a discrete wavelet transform and an analysis of geometric components content inside the obtained representations. A man-aided software using these texture features allows us to segment 3D ultrasound images.

No description available.

The purpose of this thesis is to compare the products of two different work flows in a practical environment. The work flows in question are those of building environments using super-modular textures versus the more conventional method of unique textures. The tests will try to establish whether or not the theory of the super-modular work flow holds up in practice, i.e. if the result is actually as optimized has the theory outlines. The data of interest is gathered through tests in the Unreal Development Kit, which is a free version of the commercial Unreal engine. Results are compiled into graphs in order to give a clear overview of the differences between the two products. The results show that in the context of the tests performed the super-modular workflow allocates less memory than what can be achieved using uniquely mapped assets and that the average draw calls remain the same regardless of method.

This thesis work presents a simple and practical technique for seamlessly texturing quadrilateral meshes. Using this technique, an isotropic homogeneous texture can be mapped to any quadrilateral mesh without any discontinuity or singularity in the resultant texturing. The method involves organizing a set of square texture tiles that satisfy specific boundary conditions into one texture image file which is called a tiled texture. Based on the tiled textures, we have developed an extremely simple texture mapping algorithm that randomly assigns one tile to every patch in any given quadrilateral mesh. The mapping technique developed yields singularity free textures, regardless of the singularities existing in the quadrilateral mesh, gives seamless and continuous boundaries across textures and provides an aperiodic and interesting look to the entire textured surface.

Cette thèse s'inscrit dans le thème du rendu expressif qui vise à définir des outils de création et de traitement d'images ou d'animations stylisées. Les applications concernent tous les métiers nécessitant une représentation visuelle plus stylisée qu'une photographie : création artistique (jeux vidéo, film d'animation, dessins animés), restitution archéologique, documentation technique, etc. Un critère fondamental de qualité d'une image est l'absence d'artefacts visuels. Cette considération a toujours existé, mais elle est particulièrement importante dans le cas de l'informatique graphique. En effet, la nature même de l'image – des pixels discrets – est source d'artefacts. Les artefacts sont encore plus visibles lorsque l'on s'intéresse aux animations, des artefacts temporels s'ajoutant aux artefacts spatiaux. L'objectif de cette thèse est d'une part de formaliser et mesurer ces artefacts en tenant compte de la perception humaine, et d'autre part de proposer de nouvelles méthodes de stylisation interactive d'animations 3D. Nous présentons tout d'abord un ensemble de techniques pour créer et assurer la cohérence de dessins au trait extraits de scènes 3D animées. Nous proposons ensuite deux méthodes de stylisation des régions de couleur permettant la créations d'un grand nombre de motifs. Le point commun à toutes ces approches est la représentation du médium simulé (pigment d'aquarelle, coup de crayon ou de pinceau...) par une texture évoluant au cours de l'animation. Nous décrivons enfin deux expériences utilisateurs visant à évaluer perceptuellement la qualité des résultats produits par ce type de techniques. / This PhD thesis deals with expressive rendering, a sub-field of computer graphics which aims at defining creation and processing tools to stylize images and animations. It has applications in all the fields that need depictions more stylized than photographs, such as entertainment (e.g., video games, animated films, cartoons), virtual heritage, technical illustration, etc. A crucial criterion to assert the quality of an image is the absence of visual artifacts. While already true for traditional art, this consideration is especially important in computer graphics. Indeed the intrinsic discrete nature of an image can lead to artifacts. This is even more noticeable during animations, as temporal artifacts are added to spatial ones. The goal of this thesis is twofold: (1) To formalize and measure these artifacts by taking into account human perception; (2) To propose new interactive methods to stylize 3D animations. First we present a set of techniques to ensure the coherence of line drawings extracted form 3D animated scenes. Then we propose two methods to stylize shaded regions, which allow to create a wide variety of patterns. The shared ground layer of all these approaches is the use of temporally varying textures to represent the simulated media (e.g., watercolor pigments, brush strokes). Finally we describe two user studies aiming at evaluating the quality of the results produced by such techniques.

Dans le domaine de la réalité virtuelle, la mise en situation écologique des utilisateurs nécessite l’utilisation d’interfaces homme-machine capables de transmettre mais aussi restituer des informations réalistes. L’objectif de cette thèse est de réaliser une interface haptique capable de reproduire des retours d’informations kinesthésiques et tactiles, c’est à dire la reproduction des sensations de toucher virtuel. Plus précisément, ce travail vise à reproduire simultanément la forme et la texture. Pour cela nous avons réalisé un dispositif basé sur une plateforme kinesthésique capable de retourner la forme et sur une dalle tactile capable de retourner la texture. Le retour de forme est essentiellement basé sur la restitution de la courbure par l’exploration d’une surface continue, qui peut s’orienter, s’élever et se translater tout en restant toujours tangente à une forme virtuelle au point de contact ; ceci afin de respecter la principale source d’information dans la perception de forme, l’orientation de la surface locale. Quant au retour de texture, pour le réaliser, nous intégrons au dispositif une plaque tactile à frottement variable et contrôlé, développée au L2EP. Une série d’évaluations psychophysiques ont été effectuées de façon à connaître les performances de ce stimulateur couplé kinesthésique et tactile. / In the field of virtual reality, the improvement of the user immersion requires the use of human-machine interfaces capable of transmitting but also rendering the realistic information. The objective of this PhD is to develop a haptic device which can reproduce the kinaesthetic and tactile feedbacks, which is the reproduction of virtual touch sensations. Precisely, this work aims to simultaneously simulate the shape and the texture. For this purpose, we have designed a kinaesthetic platform to simulate the shape and a tactile plate to simulate the texture, and then integrated them in a compact device. For the simulation of shape, we proposed to render the curvature of shape by exploring a continuous surface that can be orientated, be elevated and be translated while always remaining tangent to a virtual shape at the contact point, in order to respect the principal source of information in the perception of shape (the orientation of the local surface). For the simulation of texture, we integrated a tactile plate developed in L2EP, which provides variable and controlled friction. Finally, we integrated the platform and the tactile plate in a device coupling kinaesthetic and tactile feedbacks that allows us to simultaneously reproduce the sensations of shape and fine texture. Several evaluations have also been performed to know the performance of the device.

A real-time self-shadowing technique is described. State of the art shadowing techniques that utilize modern hardware often require multiple rendering passes and introduce rendering artifacts. Combining separate ideas from earlier techniques which project geometry onto a plane and project imagery onto an object results in a new real-time technique for self-shadowing. This technique allows an artist to construct occluder textures and assign them to shadow planes for a self-shadowed model. Utilizing a graphics processing unit (GPU), a vertex program computes shadowing coordinates in real-time, while a fragment program applies the shading and shadowing in a single rendering pass. The methodology used to create shadow planes and write the vertex and fragment programs is given, as well as the relation to the previous work. This work includes implementing this technique, applying it to a small set of test models, describing the types of models for which the technique is well suited, as well as those for which it is not well suited, and comparing the technique’s performance and image quality to other state of the art shadowing techniques. This technique performs as well as other real-time techniques and can reduce rendering artifacts in certain circumstances.

This thesis investigates two different approaches to improving access to the Web for visually impaired people: the design of Web content; and the presentation of content. The potential for improving the design of Web content was investigated in an evaluation of the usability of the Web Content Accessibility Guidelines of the Web Accessibility Initiative. Student Web page authors used the Guidelines to adapt Web pages containing various elements (such as images and tables). These pages were collated into a Web site, which was evaluated by visually impaired people. The page authors found it difficult to find the information they required in the Guidelines document, and had difficulties with implementing the advice of the guidelines. The visually impaired people who evaluated the pages found that the extent of the accessibility of the different elements varied depending on the individual’s experience of using the Web, and the software they used. The accessibility of some elements was not improved by the implementation of the guidelines. The potential for improving the presentation of Web content was investigated using a haptic device. The perception of virtual textures and objects by blind and sighted people via this device was examined. It was found that the virtual textures were perceived differently to the real textures examined in the literature, and that the blind people could better discriminate between the textures than the sighted people could. The virtual objects were explored from the inside and from the outside. It was found that objects generally felt larger from the inside than from the outside. This has been termed the ‘Tardis’ effect. The thesis concludes that it is difficult to define what we mean by ‘accessibility’. Without a clear definition it is not possible to judge whether a Web site is ‘truly’ accessible. The difficulties in making Web content fully accessible mean that additional methods are required for presenting the content in different ways. The researcher believes that haptic devices offer one such method, and could be particularly useful in presenting information that is visual in nature, such as information laid out in columns.

Made available in DSpace on 2014-06-12T15:56:56Z (GMT). No. of bitstreams: 2 arquivo3093_1.pdf: 6869100 bytes, checksum: 84babf04dc9aa424f94c497c190576d6 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2010 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Nós apresentamos um método eficiente para síntese de padrões definidos como uma coleção de elementos vetoriais bidimensionais, a partir de uma amostra do padrão. Soluções recentes para este problema fazem uso de triangulação da entrada ou de medidas estatísticas da amostra para controlar o estágio de síntese. Nós propomos um método aplicável a texturas coloridas, desde regular até estocásticas, e que provê controle local sobre a densidade dos elementos. A amostra é segmentada em grupos de elementos similares e definimos uma nova métrica, que não ignora elementos isolados, para cálculo de distância entre vizinhanças de elementos, para comparar vizinhanças diferentes e incompletas. O laço principal de síntese consiste em um crescimento procedural, onde sementes são substituídas por referências a elementos da amostra, gerando novas sementes até que o espaço de síntese seja preenchido. Os resultados mostram a mesma qualidade visual de trabalhos anteriores, e resolvem padrões não abordados em trabalhos anteriores. Nós também mostramos que este método pode ser estendido para sintetizar padrões vetoriais sobre malhas poligonais