Complex skeletal implicit surfaces

Recent research has demonstrated the effectiveness of complex skeletal primitives such as subdivision curves and surfaces in implicit surface modeling. This paper presents a hierarchichal modeling system with an automatic levels of detail management for a simpler modeling with an accelerated rendering. We manage levels of detail with smooth transitions and tree optimizations speeding up visualization by an order of magnitude, which allows an interactive editing of the shapes

Fractal/wavelet model as a deformation tool

A Fractal model equipped with detail concept like that used in wavelettransforms is introduced and used to perform global and local deformationsto objects. This fractal model based on Projected IFS attractorsallows the definition of free form fractal shapes controlled by a set ofpoints. The details concept taken from wavelet theory represents the geometric texture of the object. An approximation step is first done to fit themodel to the object, this step is formulated as a non-linear fitting problemand resolved using a modified Levenberg-Marquardt minimizationmethod. Global deformation can be achieved by moving control points orscaling and/or rotating the details extracted from the object. In the samemanner local deformation can be applied with additional control points.In this work, we focus on 2D curves

Fast processing of triangle meshes using triangle fans

International audienceThis paper presents a technique for decomposing a triangulated model into a set of triangle fans. We show that the triangle fan representation improves the performance of several fundamental geometric algorithms operating over triangle meshes. We present two accelerated algorithms, one for computing the nearest intersection between a ray and a fan of triangles, and one for computing the Euclidean distance from a point to a fan of triangles. We demonstrate the effectiveness of the triangle fan representation in several applications, including collision detection, implicit surface modeling and fast ray-tracing

Contributions à l'introduction de flexibilité dans la reconstruction et l'édition de modèles 3D

Cette thèse s'inscrit dans la problématique générale de la modélisation géométrique de formes libres en trois dimensions. Dans le cadre du projet Art3D (ACI Masses de Données), nous avons exploré deux directions de recherche relatives à la représentation d'objets numérisés, avec un objectif de flexibilité : la reconstruction dynamique de surface et la modélisation multireprésentation. Dans la première partie de la thèse, nous présentons une approche combinatoire flexible de la reconstruction de surface permettant de produire directement une surface triangulée simplifiée à partir d'un échantillon de points dense. La surface reconstruite peut ensuite être mise à jour de manière dynamique en ajoutant ou en retirant des données localement. La seconde partie de la thèse est consacrée à l'étude d'un modèle géométrique hybride destiné à la création de formes complexes à partir d'objets numérisés ou de primitives simples. Nous avons développé un arbre de construction permettant de combiner de manière cohérente des surfaces implicites, des maillages polygonaux et des nuages de pointsThis thesis deals with geometric modeling of complex 3D free-form shapes. In the context of the Art3D project (ACI Masses de Données), we have investigated two research directions related to the representation of digitized objects, with a flexibility goal: dynamic surface reconstruction and multirepresentation modeling. In the first part of the thesis, we introduce a flexible combinatorial approach to surface reconstruction that makes it possible to directly generate a simplified triangulated surface from a dense input point set. The reconstructed surface can be next locally refined or coarsened in a dynamic fashion. The second part presents a hybrid modeling framework for creating complex shapes from scanned models or simple primitives. We have developed an extended CSG tree that mixes implicit surfaces, polygonal meshes, and point set models in a coherent fashionLYON1-BU.Sciences (692662101) / SudocSudocFranceF

Complex skeletal implicit surfaces

Recent research has demonstrated the effectiveness of complex skeletal primitives such as subdivision curves and surfaces in implicit surface modeling. This paper presents a hierarchichal modeling system with an automatic levels of detail management for a simpler modeling with an accelerated rendering. We manage levels of detail with smooth transitions and tree optimizations speeding up visualization by an order of magnitude, which allows an interactive editing of the shapes

Modeling cracks and fractures

International audienceThis paper presents an interactive method for modeling cracks and fractures over a variety of materials such as glass, metal, wood, and stone. Existing physically based techniques are computationally demanding and lack control over the fracture propagation. Our approach consists in editing 2D fracture pattern and profile curves which are stored in an atlas according to material type. The fracture model is then automatically mapped onto the surface of the object and fractures are created by carving out a procedurally generated swept volume. Because the objects need not be voxelized or tetrahedralized as with physically based techniques, we are not limited in resolution when creating the geometry of cracks, which enables us to model small or very thin fractures

Insertion de détail dans des figures autosimilaires

National audienceThis paper deals with the approximation of natural objects using a fractal model equipped with a detail conceptlike wavelet transforms. The fractal model is a projected Iterated Function System (IFS) model. This model unifiesthe IFS model and a classical model used in computer graphics (free form representation with control points). Theconcept of wavelet transforms is used for adding a detail part to the fractal model. The approximation problemhas a two steps formulation : a nonlinear fitting optimisation of the fractal model and a linear transform for thecomputation of the detail coefficients. We have used this approximation method to approximate two leaves border.Then, the detail concept has been used to transfer the geometric texture from one leaf to another, and also toamplify these geometric details.Cet article traite de l’approximation d’objets naturels grâce à un modèle fractal équipé d’un concept de détailcomme celui présent dans les ondelettes. Le modèle fractal est un modèle IFS (Iterated Function System) projeté.Ce modèle unifie le modèle IFS et un modèle classique utilisés en infographie (déformation des objets grâce àdes points de contrôle). Le concept des transformations par ondelettes est immité par l’ajout d’une partie dedétail au modèle fractal. L’approximation se fait alors en deux phases : une phase d’optimisation non linéairedu modèle fractal et une phase de transformation linéaire qui permet de calculer les coefficients de détail. Nousavons employé cette méthode pour approximer la frontière de deux feuilles. Le concept de détail a ensuite étéemployé pour transférer la texture géométrique d’une feuille à une autre, ainsi que pour l’amplification de détailsgéométriques

A flexible framework for surface reconstruction from large point sets

International audienceThis paper presents a flexible method to reconstruct simplified mesh surfaces from large unstructured point sets, extending recent work on dynamic surface reconstruction. The method consists of two core components: an efficient selective reconstruction algorithm, based on geometric convection, that simplifies the input point set while reconstructing a surface, and a local update algorithm that dynamically refines or coarsens the reconstructed surface according to specific local sampling constraints.A new data structure is introduced that significantly accelerates the original selective reconstruction algorithm and makes it possible to handle point set models with millions of sample points. This data structure mixes a kd-tree with the Delaunay triangulation of the selected points enriched with a sparse subset of landmark sample points. This design efficiently responds to the specific spatial location issues of the geometric convection algorithm. It also permits the development of an out-of-core implementation of the method, so that simplified mesh surfaces can be seamlessly reconstructed and interactively updated from point sets that do not fit into main memory