Query: "Marie-Paule Cani"

title: Interactive Flat Coloring of Minimalist Neat Sketches
abstract: We introduce a simple Delaunay triangulation based algorithm for the interactive coloring of neat line art minimalist sketches, ie. vector sketches that may include open contours. The main objective is to minimize user intervention and make interaction as natural as with the flood fill algorithm while extending coloring to regions with open contours. In particular, we want to save the user from worrying about parameters such as stroke weight and size. Our solution works in two steps, 1) a segmentation step in which the input sketch is automatically divided into regions based on the underlying Delaunay structure and 2) the interactive grouping of neighboring regions based on user input. More precisely, a region adjacency graph is computed from the segmentation result, and is interactively partitioned based on user input to generate the final colored sketch. Results show that our method is as natural as a bucket fill tool and powerful enough to color minimalist sketches.

title: Interactive Meso scale Simulation of Skyscapes
abstract: Although an important component of natural scenes, the representation of skyscapes is often relatively simplistic. This can be largely attributed to the complexity of the thermodynamics underpinning cloud evolution and wind dynamics, which make interactive simulation challenging. We address this problem by introducing a novel layered model that encompasses both terrain and atmosphere, and supports efficient meteorological simulations. The vertical and horizontal layer resolutions can be tuned independently, while maintaining crucial inter layer thermodynamics, such as convective circulation and land air transfers of heat and moisture. In addition, we introduce a cloud form taxonomy for clustering, classifying and upsampling simulation cells to enable visually plausible, finely sampled volumetric rendering.

title: Exploring robust locomotion control on dynamically evolving grounds
abstract: The design of motion controllers for physically based virtual creatures is a key task for many applications. They can be used to enhance the realism of 3D films or to create plausible reactive characters for video games. In a more scientific basis, controlled characters can be used for computing visual simulations from priors. More specifically, the present work is motivated by a collaboration between our Computer Graphics group and a team of Prehistorians studying the behaviour of the early humans who lived in the Tautavel valley (south of France) 350 000 years ago. This collaboration raises many interesting questions such as: Could we infer locomotion styles for these early humans from those of modern humans and the well studied differences of morphology? How did the early humans interact with the natural environment surrounding them (including rocks, grass, sliding gravels, mud, rivers to be crossed) The long term goal being to provide an immersive simulation tool where prehistorians would get visual feedback from their expressed knowledge and hypotheses on early human behaviour, such as being able to follow a prehistoric man wandering about in a typical day.

title: Voxels Stones Sand Rock Air Layer stacks with overhangs
abstract: Terrains are a crucial component of three dimensional scenes and are present in many Computer Graphics applications. Terrain modeling methods focus on capturing landforms in all their intricate detail, including eroded valleys arising from the interplay of varied phenomena, dendritic mountain ranges, and complex river networks. Set against this visual complexity is the need for user control over terrain features, without which designers are unable to adequately express their artistic intent. This article provides an overview of current terrain modeling and authoring techniques, organized according to three categories: procedural modeling, physically based simulation of erosion and land formation processes, and example based methods driven by scanned terrain data. We compare and contrast these techniques according to several criteria, specifically: the variety of achievable landforms; realism from both a perceptual and geomorphological perspective; issues of scale in terms of terrain extent and sampling precision; the different interaction metaphors and attendant forms of user control, and computation and memory performance. We conclude with an in depth discussion of possible research directions and outstanding technical and scientific challenges.

title: Untangling Layered Garments: An Implicit Approach
abstract: The efficient animation of layers of garments is a challenging task, as it requires handling collisions and contacts between multiple thin surfaces, which may be difficult to untangle once inter penetrations have occurred. We propose a novel geometric approach, based on implicit surfaces, to robustly handle such situations. At each animation step, our method converts the possibly intersecting garment surfaces to an implicit representation. They are then combined using a new binary operator that guarantees, as output, collision free states of the surfaces. In addition to a precise modeling of contact situations, our method enables to model the relative influence of each cloth layer, based on their relative stiffnesses and thicknesses.

title: Toiles 3D interactives pour une ebauche du grossier aux details Application au design conceptuel en architecture
abstract: En cette ere numerique, les architectes realisent des aller retours entre le croquis papier et les logiciels numeriques. Par consequence, notre objectif est de proposer une methode permettant une esquisse du grossier aux details et la prise en compte de l'incertitude dans un outil adapte au design en architecture. Notre solution repose sur un nouveau concept de toiles 3D interactives. Plus specifiquement, nos contributions sont des toiles 3D utilisees comme volume englobant pour la creation, l'affichage et l'interaction interactifs du grossier au details dans une "pelure d'oignon" et la possibilite de gerer l'incertitude par une navigation parmi les differentes options esquissees par l'utilisateur. Une etude utilisateur realisee avec des architectes professionnels a mis en evidence l'interet d'un tel systeme pour la conception architecturale.

title: Interactive 3D canvases for a coarse to fine sketching Application to conceptual design in architecture
abstract: In this digital age, architects usually alternate between paper sketch and digital softwares. Therefore, our goal is to propose a method enabling coarse to fine sketching and representation of uncertainty in a tool adapted to architectural design. Our solution is based on a new concept of interactive 3D canvases. More specifically, our contributions are 3D canvases used as bounding volume for interactive coarse to fine creation, display and interaction in "onion peel" and the possibility to manage uncertainty by a navigation through the different options sketched by the user. A user study conducted with architects highlighted the interest of such a system in conceptual architectural design.

title: N A 24 J ul 2 00 6 A Vortex Method for Biphasic Fluids Interacting with Rigid Bodies
abstract: We present an accurate Lagrangian method based on vortex par icles, level sets, and immersed boundary methods, for animating the interplay between two fluids and r igi solids. We show that a vortex method is a good choice for simulating bi phase flow, such as liquid a n gas, with a good level of realism. Vortex particles are localized at the interfaces between the two flu ids and within the regions of high turbulence. We gain local precision and efficiency from the stable advect ion permitted by the vorticity formulation. Moreover, our numerical method straightforwardly solves t he two way coupling problem between the fluids and animated rigid solids. This new approach is validated th rough numerical comparisons with reference experiments from the computational fluid community. We also sh w that the visually appealing results obtained in the CG community can be reproduced with increase d efficiency and an easier implementation.

title: Une approche implicite pour la modelisation de couches de vetements
abstract: Animer des vetements superposes est difficile a cause des collisions entre les couches en contact sur de grandes surfaces, qui doivent de surcroit se plisser pour maintenir leur isometrie. Le but de notre travail est de representer chaque couche de vetements par une surface implicite, puis de melanger les champs associes a l'aide d'un opera teur qui modelise les interactions statiques entre couches et corrige les intersections. Notre solution se base sur l'utilisation de plusieurs isosurfaces de champs scalaires pour approximer le corps et les vetements. La modelisation des plis de ces derniers est directement integree dans ce modele volumique grace a des deformeurs du champ. Les operateurs de melange que nous presentons permettent ensuite la correction des intersections eventuelles, en prenant en compte l'influence relative de chacun des vetements sur les autres. Cette influence depend dans notre modele d'un parametre modelisant la rigidite relative des tissus. Nous validons cette approche dans un cas d'ecole en 2D et montrons de premiers resultats 3D.

title: Progressive and Efficient Multi Resolution Representations for Brain Tractograms
abstract: Current tractography methods generate tractograms composed of millions of 3D polylines, called fibers, making visualization and interpretation extremely challenging, thus complexifying the use of this technique in a clinical environment. We propose to progressively simplify tractograms by grouping similar fibers into generalized cylinders. This produces a fine grained multiresolution model that provides a progressive and real time navigation through different levels of detail. This model preserves the overall structure of the tractogram and can be adapted to different measures of similarity. We also provide an efficient implementation of the method based on a Delaunay tetrahedralization. We illustrate our method using the Human Connectome Project dataset.