Le but de cette thèse est de faciliter et d'accélérer le dessin pour les amateurs ainsi que pour les dessinateurs experts en utilisant des techniques de traitement d'image et d'interaction. Nous identifions trois problèmes spécifiques liés au dessin, et proposons des outils pour aider les utilisateurs à surmonter les principaux défis sur chaque domaine. Dans le chapitre 2, nous présentons un outil de dessin interactif pour aider des débutants à pratiquer les techniques traditionnelles de dessin par observation. Nous construisons cet outil autour de techniques traditionnelle. Nous extrayons automatiquement des guides visuels à partir d'une photographie. L'interface de l'outil affiche ces informations et offre un retour pour guider l'utilisateur dans la reproduction du dessin. Dans le chapitre 3, nous proposons un outil qui permet aux utilisateurs de créer des bijoux par pliage de fils de fer. Cette forme de bijoux faits à la main peut être considérée comme une forme de dessin à base de fil de fer. La méthode présentée aide l'utilisateur dans les principaux défis de la création de bijoux à partir d'un dessin: la décomposition de l'entrée dans un ensemble de fils, et le pliage des fils pour leur donner forme. Dans le chapitre 4, nous proposons une méthode pour aider les designers à enrichir leurs dessins avec de la couleur et de l'ombrage. Les designers tracent souvent des lignes de courbure pour représenter la forme des surfaces lisses dans des esquisses. Nous exploitons cette information et extrapolons les lignes de courbure dans le design. Cette extrapolation nous permet d'estimer la courbure 3D du dessin, pour créer des ombres et des textures sur l'esquisse. / The goal of this thesis is to facilitate and accelerate drawing for amateurs as well as for expert designers and illustrators, employing computer graphics, image processing and interaction techniques. As this is a broad spectrum to tackle, we identify three specific problems related to drawing and propose computer tools to help users overcome the main challenges on each domain. In Chapter 2 we present an interactive drawing tool to help beginners practice drawing-by-observation techniques. We build on a number of traditional techniques to help people gain consciousness of the shapes in a scene. We automatically extract visual guides from a model photograph and offer corrective feedback to guide their reproduction in the drawing. In Chapter 3 we propose a tool that helps users create wire wrapped jewelry. This technique of handmade jewelry can be seen as a form of line drawing with metal wires. The presented method assist the user in the main challenges of creating 2D wire-wrapped jewelry from a drawing: decomposing the input into a set of wires, and bending the wires to give them shape. In Chapter 4 we propose a method to help designers enrich their drawings with color and shading. Professionals frequently draw curvature lines to convey bending of smooth surfaces in concept sketches. We exploit this information and extrapolate curvature lines in a rough concept sketch. This extrapolation allows us to recover the intended 3D curvature and surface normal at each pixel, which we use to compute shading and texturing over the sketch.

Supporting user designs of 3D contents remains a challenge in geometric modeling. Various modeling tools have been developed in recent years to facilitate architectural designs and artistic creations. However, these tools require both modeling skills and raw creativity. Instead of creating models from scratch, one of the most popular choices is to extract intrinsic patterns from exemplar inputs (e.g., shape collections and sketches), to produce creative models while preserving the patterns. The mod- eling process contains two main stages, analysis and synthesis. The analysis of input models is usually performed at component level, especially for man-made objects that can be decomposed into several semantic parts, for example, the seat and handles of a bicycle. The synthesis stage recombines parts of shapes to generate new models that usually have topological or geometric variations. In this thesis, we propose three design tools aimed at easing the modeling process. We focus on man-made objects and scenes such as buildings and furniture, as the functionality of such shapes can be analyzed at the component level. A relation graph, which is commonly used in shape analysis, can then be built to represent the input shapes. In our work, the graph nodes denote the elements of a model (i.e., rooms, shape parts, and strokes respectively), while the edges capture the intrinsic relations between connected elements. With the use of graph representations, we extract and present controllable components to users for supporting their designs. The emphasis of our work is on three aspects. Firstly, we propose a framework for supporting interior layout design, which allows users to manipulate the produced floor plans, i.e., changing the scales of rooms and their positions as well. When the user modifies the topology of a layout, the corresponding layout graph is updated and the room geometries are optimized under certain constraints, e.g., user specified scales, the adjacency of rooms, and fabrication considerations (i.e., economic construction cost). Secondly, we introduce replaceable substructures as arrangements of shape components that can be interchanged while ensuring boundary consistency. Based on the shape graphs that encode the structures of input models, we propose new automatic operations to discover replaceable substructures across models or within a model. We enforce a pair of subgraphs matching along their boundaries so that switching two subgraphs results in topological variations. Thirdly, we develop an interactive system that supports a freeform design by interpreting user sketches. 3D contents can be extracted from input strokes with or without user annotations. Our system accepts user strokes, analyzes their contacts and vanishing directions with respect to an anchored image, and projects 2D strokes to 3D space via a multi- stage optimization on spatial canvas selection. We demonstrate the computational approaches on a range of example models and design studies.

La modélisation à l'aide de croquis a pour but de construire une forme tridimensionnelle à partir d'un dessin en deux dimensions. L'utilisateur dessine la silhouette de l'objet à reconstruire sur le plan de dessin, puis un algorithme génère automatiquement une forme en 3D à partir de ce croquis. La modélisation par croquis à l’avantage d’être plus simple et plus rapide que la modélisation classique qui requiert l’utilisation de logiciels complexes comme 3DS Max, Maya, Blender, etc. Les applications liées à la modélisation par croquis seraient nombreuses : dans le domaine de l'infographie, la modélisation géométrique pour les jeux vidéo le dessin industriel, les effets spéciaux, etc., serait plus rapide et moins coûteuse. La modélisation à l’aide de croquis pourrait être utilisée par tout le monde. Nous avons tous, un jour ou l’autre, fait un croquis pour expliquer le chemin à prendre pour aller à un lieu précis, un croquis pour l’agencement d’une cuisine et d’une salle de séjour, ou un croquis pour expliquer le fonctionnement d’une machine, etc. Dans ce mémoire de thèse, nous nous intéressons dans un premier temps au problème de la génération de courbes en 3D constituées d’hélices à partir de croquis. Nous présentons deux algorithmes qui traitent ce problème. Puis dans un second temps, nous nous intéressons à la génération de surfaces à partir de croquis et plus particulièrement à la génération de bas-reliefs, ces surfaces ayant l’avantage de ne pas présenter de parties cachées. / The goal of sketch based modeling is to generate a 3D shape from a 2D sketch. The user draw the outline of the object to rebuild on the sketch plane, then an algorithm automatically build the 3D shape from the sketch. Sketch based modeling is easier to use and faster than traditional technics which uses complex modeling software such as 3DS max, Maya or Blender. There is a lot of applications for sketch based modeling, for example, the geometric modeling for video games, industrial design, special effects, etc. would be faster and less expensive. Sketch based modeling can be used by anybody. We all , at one time or another , made a sketch to explain a route to take to get to a specific place , a sketch for the arrangement of a kitchen and a living room, or sketches to explain the operation of a machine, etc. In this thesis memory, we look initially to the problem of generating piecewise helix curves from 2D sketches . We present two algorithms that address this problem. Then in a second step, we focus on the generation of 3D surfaces from sketches and more particularly to the generation of low reliefs, these surfaces have the advantage of not presenting hidden parts.

This thesis is concerned with the study of how sketch-based systems can be improved to enhance idea generation process in conceptual design stage. It is also concerned with achieving a kind of integration between sketch-based systems and CAD systems to complete the digitization of the design process as sketching phase is still not integrated with other phases due to the different nature of it and the incomplete digitization of sketching phase itself. Previous studies identified three main related issues: sketching process, sketch-based modeling, and the integration between the digitized design phases. Here, the thesis is motivated from the desire to improve sketch-based modeling to support idea generation process but unlike previous studies that only focused on the technical or drawing part of sketching, this thesis attempts to concentrate more on the mental part of the sketching process which play a key role in developing ideas in design. Another motivation of this thesis is to produce a kind of integration between sketch-based systems and CAD systems to enable 3D models produced by sketching to be edited in detailed design stage. As such, there are two main contributions have been addressed in this thesis. The first contribution is the presenting of a new approach in designing sketch-based systems that enable more support for idea generation by separating thinking and developing ideas from the 3D modeling process. This kind of separation allows designers to think freely and concentrate more on their ideas rather than 3D modeling. the second contribution is achieving a kind of integration between gesture-based systems and CAD systems by using an IGES file in exchanging data between systems and a new method to organize data within the file in an order that make it more understood by feature recognition embedded in commercial CAD systems.

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