Procedural 3D Caves, Clouds and Architecture Generation Method Based on Shape Grammar and Morphing

This paper presents a new procedural 3D modelconstructionalgorithm that benefits from a combination ofdiscrete and continuous modeling approaches. Our algorithmmodels complex scene components such as caves, architecturalbuildings, and clouds. The method combines the discretedescriptiveness of shape grammars with the continuous flexibilityof shape morphing. This combination allows for a modelingapproach that can be controlled by a morphing parameter toproduce various types of geometry. In the paper, we focus on thedescription of the algorithm while also showing its capabilities ingenerating complex scene components

Echantillonnage anisotropique et rendu par points différentiels pour les surfaces implicites

Dans cet article, nous proposons une solution adaptant aux surfaces implicites, le rendu par points différentiels ("differential point rendering") de Kalaiah et Varshney [KV01] originellement développé pour les surfaces paramétriques et les maillages triangulaires. La principale difficulté pour cette adaptation est que les deux étapes du processus d'échantillonnage proposé dans [KV01] s'appuient fortement sur des relations de voisinage entre les échantillons, voisinage qui n'existe pas naturellement pour les surfaces implicites. Pour résoudre ce problème, nous proposons d'étudier les possibilités d'extensions de la technique d'échantillonnage par particules de Witkin et Heckbert [WH94] afin de prendre en compte les directions et les valeurs des courbures principales de la surface implicite. Ainsi, nous présenterons des résultats provenant d'une utilisation de particules ellipsoïdales ainsi que les problèmes inhérents à la nature même de l'ellipsoïde. Puis nous proposerons de nouvelles directions de recherche dans le but de résoudre ces problèmes

Meshing implicit surfaces with certified topology title

We describe a new algorithm for building piecewise linear approximations of an implicit surface. This algorithm is the first one guaranteeing that the implicit surface and its approximation are isotopic

Poligonização de Superfícies Implícitas por Amostragem Baseada num Corrector de Newton

A maioria dos algoritmos para amostragem de superfícies implícitas baseia-se no Teorema do Valor Intermédio. Isto é, assume-se que existe variação de sinal da função que representa a superfície. Acontece que nem sempre é assim, ou seja, nem sempre existe variação de sinal da função na vizinhança da superfície. Introduz-se assim um novo algoritmo baseado num Corrector de Newton capaz de efectuar a amostragem de superfícies implícitas quer exista ou não variação de sinal da função na vizinhança da superfície.Most algorithms for sampling implicit surfaces are based on the Intermediate Value Theorem. That is, it is assumed that the function that describes a surface changes sign in the neighborhood of each point of it. It happens that not all functions describing implicit surfaces change sign in the neighborhood of each surface point. We introduce a new Newton-Corrector based algorithm capable of sampling implicit surfaces, regardless whether there exists sign changes near the surface or not

Correspondence of three-dimensional objects

First many thanks go to Prof. Hans du Buf, for his supervision based on his experience, for providing a stimulating and cheerful research environment in his laboratory, for letting me participate in the projects that produced results for papers, thus made me more aware of the state of the art in Computer Vision, especially in the area of 3D recognition. Also for his encouraging support and his way to always nd time for discussions, and last but not the least for the cooking recipes... Many thanks go also to my laboratory fellows, to Jo~ao Rodrigues, who invited me to participate in FCT and QREN projects, Jaime Carvalho Martins and Miguel Farrajota, for discussing scienti c and technical problems, but also almost all problems in the world. To all persons, that worked in, or visited the Vision Laboratory, especially those with whom I have worked with, almost on a daily basis. A special thanks to the Instituto Superior de Engenharia at UAlg and my colleagues at the Department of Electrical Engineering, for allowing me to suspend lectures in order to be present at conferences. To my family, my wife and my kids

Interactive freeform editing techniques for large-scale, multiresolution level set models

Level set methods provide a volumetric implicit surface representation with automatic smooth blending properties and no self-intersections. They can handle arbitrary topology changes easily, and the volumetric implicit representation does not require the surface to be re-adjusted after extreme deformations. Even though they have found some use in movie productions and some medical applications, level set models are not highly utilized in either special effects industry or medical science. Lack of interactive modeling tools makes working with level set models difficult for people in these application areas.This dissertation describes techniques and algorithms for interactive freeform editing of large-scale, multiresolution level set models. Algorithms are developed to map intuitive user interactions into level set speed functions producing specific, desired surface movements. Data structures for efficient representation of very high resolution volume datasets and associated algorithms for rapid access and processing of the information within the data structures are explained. A hierarchical, multiresolution representation of level set models that allows for rapid decomposition and reconstruction of the complete full-resolution model is created for an editing framework that allows level-of-detail editing. We have developed a framework that identifies surface details prior to editing and introduces them back afterwards. Combining these two features provides a detail-preserving level set editing capability that may be used for multi-resolution modeling and texture transfer. Given the complex data structures that are required to represent large-scale, multiresolution level set models and the compute-intensive numerical methods to evaluate them, optimization techniques and algorithms have been developed to evaluate and display the dynamic isosurface embedded in the volumetric data.Ph.D., Computer Science -- Drexel University, 201

Vector Field Based Texture Mapping of Animated Implicit Objects

International audienceThis paper shows that an adequate use of vector fields can solve most inconsistencies related to texture mapping that appear in current animation and rendering systems based on implicit objects. The method used is based on the concept of a virtual skin. A skin with its own texture mapping is spread over an implicit object and is constrained to stick to the deformation of the implicit object. A vector field is used to compute the relationship between the motion of the skin and the deformation of the object. Visual and implementation issues are discussed with respect to typical applications of implicit objects in computer graphics