International audienceThis paper presents a diffusion method for generating terrains from a set of parameterized curves that characterize the landform features such as ridge lines, riverbeds or cliffs. Our approach provides the user with an intuitive vector-based feature-oriented control over the terrain. Different types of constraints (such as elevation, slope angle and roughness) can be attached to the curves so as to define the shape of the terrain. The terrain is generated from the curve representation by using an efficient multigrid diffusion algorithm. The algorithm can be efficiently implemented on the GPU, which allows the user to interactively create a vast variety of landscapes

This paper presents several improvements to the marching triangles algorithm for general implicit surfaces. The original method generates equilateral triangles of constant size almost everywhere on the surface. We present several modifications to adapt the size of the triangles to the curvature of the surface. As cracks may arise in the resulting polygonization, we propose a specific crack‐closing method invoked at the end of the mesh growing step. Eventually, we show that the marching triangles can be used as an incremental meshing technique in an interactive modeling environment. In contrast to existing incremental techniques based on spatial subdvision, no extra data‐structure is needed to incrementally edit skeletal implicit surfaces, which saves both memory and computation time.

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This paper addresses the metamorphosis of soft objects built from skeletons. W e propose a new approach that may be split into three steps. The first step consists in an original splitting of the initial and the final shapes with a view to creating a bijective graph of correspondence. In the second step, we assume that the skeletons are convex polygonal shapes, and thus take advantage of the properties of Minkowski sums to characterize the skeletons of intermediate shapes. Eventually, we characterize the intermediate distance and field functions; we describe a set of interpolation methods and propose to use a restricted class of parametrized distance and field functions so as to preserve coherence and speed-up computations. W e show that we can easily extend those results to achieve a Bézier like metamorphosis where control points are replaced b y control soft objects; in this scope, we have adapted existing accelerated techniques that build a Bézier transformation from a set of convex polyhedra to any kind of convex polygonal shapes. Eventually, we point out that matching all components of the initial and the final shapes generates amorphous intermediate shapes based on an overwhelming number of intermediate sub-components. Thus, we propose heuristics with a view to preserving coherence during the transformation and accelerating computations. W e have implemented and tested our techniques in an experimental ray-tracer.

Reconstruction of a simplified meshLocal dynamic reconstruction refinement Figure 1. Our reconstruction framework, illustrated on the TRIPLE HECATE model. Starting from a dense input point set, we reconstruct a simplified mesh (center). Benefiting from the connectivity of this initial reconstruction, we can make it to evolve dynamically so as to refine the approximation locally. This refinement can be achieved either in an automatic fashion, for example in order to improve the quality of the elements of the mesh, or interactively, in order to add or remove sample points. Here, the draped dress has been locally enhanced (right). AbstractIn this paper, we introduce a flexible framework for the reconstruction of a surface from an unorganized point set, extending the geometric convection approach introduced by Chaine [9]. Given a dense input point cloud, we first extract a triangulated surface that interpolates a subset of the initial data. We compute this surface in an output sensitive manner by decimating the input point set on-the-fly during the reconstruction process. Our simplification procedure relies on a simple criterion that locally detects and reduces oversampling. If needed, we then operate in a dynamic fashion for local refinement or further simplification of the reconstructed surface. Our method allows to locally update the reconstructed surface by inserting or removing sample points without restarting the convection process from scratch. This iterative correction process can be controlled interactively by the user or automatized given some specific local sampling constraints.

The preprocessing of large meshes to provide and optimize interactive visualization implies a complete reorganization that often introduces significant data growth. This is detrimental to storage and network transmission, but in the near future could also affect the efficiency of the visualization process itself, because of the increasing gap between computing times and external access times. In this article, we attempt to reconcile lossless compression and visualization by proposing a data structure that radically reduces the size of the object while supporting a fast interactive navigation based on a viewing distance criterion. In addition to this double capability, this method works out-of-core and can handle meshes containing several hundred million vertices. Furthermore, it presents the advantage of dealing with any n-dimensional simplicial complex, including triangle soups or volumetric meshes, and provides a significant rate-distortion improvement. The performance attained is near state-of-the-art in terms of the compression ratio as well as the visualization frame rates, offering a unique combination that can be useful in numerous applications.