Unsupervised Polygonal Reconstruction of Noisy Contours by a Discrete Irregular Approach

International audienceIn this paper, we present an original algorithm to build a polygonal reconstruction of noisy digital contours. For this purpose, we first improve an algorithm devoted to the vectorization of discrete irregular isothetic objects. Afterwards we propose to use it to define a reconstruction process of noisy digital contours. More precisely, we use a local noise detector, introduced by Kerautret and Lachaud in IWCIA 2009, that builds a multi-scale representation of the digital contour, which is composed of pixels of various size depending of the local amount of noise. Finally, we compare our approach with previous works, by con- sidering the Hausdorff distance and the error on tangent orientations of the computed line segments to the original perfect contour. Thanks to both synthetic and real noisy objects, we show that our approach has interesting performance, and could be applied in document analysis systems

Deep Generative Models on 3D Representations: A Survey

Generative models, as an important family of statistical modeling, target learning the observed data distribution via generating new instances. Along with the rise of neural networks, deep generative models, such as variational autoencoders (VAEs) and generative adversarial network (GANs), have made tremendous progress in 2D image synthesis. Recently, researchers switch their attentions from the 2D space to the 3D space considering that 3D data better aligns with our physical world and hence enjoys great potential in practice. However, unlike a 2D image, which owns an efficient representation (i.e., pixel grid) by nature, representing 3D data could face far more challenges. Concretely, we would expect an ideal 3D representation to be capable enough to model shapes and appearances in details, and to be highly efficient so as to model high-resolution data with fast speed and low memory cost. However, existing 3D representations, such as point clouds, meshes, and recent neural fields, usually fail to meet the above requirements simultaneously. In this survey, we make a thorough review of the development of 3D generation, including 3D shape generation and 3D-aware image synthesis, from the perspectives of both algorithms and more importantly representations. We hope that our discussion could help the community track the evolution of this field and further spark some innovative ideas to advance this challenging task

Courbure discrète : théorie et applications

International audienceThe present volume contains the proceedings of the 2013 Meeting on discrete curvature, held at CIRM, Luminy, France. The aim of this meeting was to bring together researchers from various backgrounds, ranging from mathematics to computer science, with a focus on both theory and applications. With 27 invited talks and 8 posters, the conference attracted 70 researchers from all over the world. The challenge of finding a common ground on the topic of discrete curvature was met with success, and these proceedings are a testimony of this wor

Interdependence of Flow and Shape Morphological Dynamics For Flow-Induced Erosion of Bluff Bodies

Flow-induced erosion encompasses all processes in which fluid-solid interactions result in the removal and transport of material from the solid. The removed material may change its physical state and/or chemical composition and may be redeposited onto the solid body or advected away by the fluid and deposited elsewhere. Common to all flow induced erosion processes is that they involve an eroding surface, and eroding agent, and a fluid flow which delivers the eroding agent to the eroding surface. Consequently, the study of erosion is difficult as it requires detailed knowledge of the material, mechanical, and/or thermophysical properties of the eroding surface; the transport mechanisms that deliver the eroding agent to the eroding surface; and the transport mechanisms that entrain and advect the eroded material into and within the fluid flow. This difficulty is compounded by the fact that that there is a feedback coupling between the eroding surface and the fluid dynamics that control the transport mechanisms important to erosion. Specifically, during erosion, surface morphological changes to the eroding surface will alter the flow field thereby increasing or decreasing the rate at which the eroding agent is delivered to the eroding surface. This in turn alters the surface morphology. Thus a complex feedback cycle exists between the fluid and surface dynamics. The study of this feedback cycle has received little attention in the fluid mechanics community. This relative neglect is understandable due to its non-equilibrium nature, yet surprising when one considers how much erosion by the action of a flow is an integral part of major scientific and engineering fields, for example geophysics, environmental, manufacturing, and aerospace. The underlying research objective of this dissertation is to better understand the two-way coupling between an eroding body and the surface flux of the eroding agent by evaluating the shape dynamics of eroding bluff bodies through the erosion process. The problem is challenging since, as described above, the surface flux of the eroding agent will vary as the surface morphology of the eroding body evolves. In order to investigate the complex interdependence between the flow and surface morphology of an eroding body during flow-induced erosion, physical ablation and dissolution experiments will be performed and existing numerical datasets will be analyzed to: (i) re-evaluate existing scaling laws regarding geometric properties (cross-sectional area, wetted perimeter, and curvature) of bluff bodies undergoing erosion in (a) uniform, unidirectional flow, (b) in spatially and temporally varying flow, and (c) in convectively driven flow; (ii) identify a shape parameter of the eroding surface that is well-correlated with local evolutional changes to the eroding agent surface flux; and (iii) develop a simple feedback erosion model that bypasses the fluid dynamics and adjusts the local eroding agent surface flux based on the evaluation of the identified shape parameter. The focus on the erosion of bluff bodies was chosen because, in principle, it is more amenable to the study of the erosion feedback cycle as the evolution of the shape dynamics and morphological changes to the surface of the eroding bluff body are a direct result of the, unknown, instantaneous magnitude of the local eroding agent surface flux. Since the evolution of the local eroding agent surface flux is a direct consequence of the feedback from the eroding surface on the flow dynamics, an improved understanding of the erosion feedback cycle is possible by evaluating only the morphological changes to the surface of the eroding bluff body

Abstracts for the twentyfirst European workshop on Computational geometry, Technische Universiteit Eindhoven, The Netherlands, March 9-11, 2005

This volume contains abstracts of the papers presented at the 21st European Workshop on Computational Geometry, held at TU Eindhoven (the Netherlands) on March 9–11, 2005. There were 53 papers presented at the Workshop, covering a wide range of topics. This record number shows that the field of computational geometry is very much alive in Europe. We wish to thank all the authors who submitted papers and presented their work at the workshop. We believe that this has lead to a collection of very interesting abstracts that are both enjoyable and informative for the reader. Finally, we are grateful to TU Eindhoven for their support in organizing the workshop and to the Netherlands Organisation for Scientific Research (NWO) for sponsoring the workshop

Collection of abstracts of the 24th European Workshop on Computational Geometry

International audienceThe 24th European Workshop on Computational Geomety (EuroCG'08) was held at INRIA Nancy - Grand Est & LORIA on March 18-20, 2008. The present collection of abstracts contains the 63 scientific contributions as well as three invited talks presented at the workshop

The 1992 NASA Langley Measurement Technology Conference: Measurement Technology for Aerospace Applications in High-Temperature Environments

An intensive 2-day conference to discuss the current status of measurement technology in the areas of temperature/heat flux, stress/strain, pressure, and flowfield diagnostics for high temperature aerospace applications was held at Langley Research Center, Hampton, Virginia, on April 22 and 23, 1993. Complete texts of the papers presented at the Conference are included in these proceedings

LIPIcs, Volume 274, ESA 2023, Complete Volume

LIPIcs, Volume 274, ESA 2023, Complete Volum