Pierre Alliez

Inria Senior Researcher
Head of science
Team Leader
3IA Côte d’Azur Chair
Project-team TITANE
Inria Sophia Antipolis – Méditerranée


Contact information
Pierre Alliez
Inria Sophia-Antipolis
2004 route des Lucioles BP 93
06902 Sophia-Antipolis cedex
Office: Y313 (Byron building)
Phone: (33) 4 92 38 76 77
Email: pierre.alliez (replace by arobas) inria.fr

My main research interests are on topics commonly referred to as Geometry Processing: geometry compression, surface approximation, mesh parameterization, surface remeshing, mesh generation and surface reconstruction. Initially considered as a subfield of Computer Graphics and Computational Geometry, Geometry Processing has developed over the last years into a whole research community seeking automatic, computerized processing of complex shapes.

I received the Eurographics Young Researcher Award 2005. I was program co-chair of the EUROGRAPHICS Symposium on Geometry Processing 2008, Pacific Graphics 2010, Geometric Modeling and Processing 2014, EUROGRAPHICS 2019 and Solid and Physical Modeling 2019.
Associate editor of the ACM Transactions on Graphics between 2010 and 2017, of Computer Graphics Forum since 2018, and of Computer Aided Design between 2019 and 2021. I have been awarded in 2011 a Starting Grant from the ERC (European Research Council), entitled “IRON”, which stands for “Robust Geometry Processing”. I have been awarded in 2017 an ERC proof of concept grant, entitled “TITANIUM” (software components for robust geometry processing).

See google scholar
– See list of publications on HAL
– See publications on dlbp
– Publications on TITANE web site

Recent publications:

Progressive Discrete Domains for Implicit Surface Reconstruction
Tong Zhao, Pierre Alliez, Tamy Boubekeur, Laurent Busé, Jean-Marc Thiery
Computer Graphics Forum, Wiley, In press, Proceedings of the EUROGRAPHICS Symposium on Geometry Processing 2021
Abstract: Many global implicit surface reconstruction algorithms formulate the problem as a volumetric energy minimization, trading data fitting for geometric regularization. As a result, the output surfaces may be located arbitrarily far away from the input samples. This is amplified when considering i) strong regularization terms, ii) sparsely distributed samples or iii) missing data. This breaks the strong assumption commonly used by popular octree-based and triangulation-based approaches that the output surface should be located near the input samples. As these approaches refine during a pre-process, their cells near the input samples, the implicit solver deals with a domain discretization not fully adapted to the final isosurface. We relax this assumption and propose a progressive coarse-to-fine approach that jointly refines the implicit function and its representation domain, through iterating solver, optimization and refinement steps applied to a 3D Delaunay triangulation. There are several advantages to this approach: the discretized domain is adapted near the isosurface and optimized to improve both the solver conditioning and the quality of the output surface mesh contoured via marching tetrahedra.
Delaunay Meshing and Repairing of NURBS Models
Xiao Xiao, Pierre Alliez, Laurent Busé, Laurent Rineau
Computer Graphics Forum, Wiley, In press, Proceedings of the EUROGRAPHICS Symposium on Geometry Processing 2021
Abstract: CAD models represented by NURBS surface patches are often hampered with defects due to inaccurate representations of trimming curves. Such defects make these models unsuitable to the direct generation of valid volume meshes, and often require trial-and-error processes to fix them. We propose a fully automated Delaunay-based meshing approach which can mesh and repair simultaneously, while being independent of the input NURBS patch layout. Our approach proceeds by Delaunay filtering and refinement, in which trimmed areas are repaired through implicit surfaces. Beyond repair, we demonstrate its capability to smooth out sharp features, defeature small details, and mesh multiple domains in contact.
StandardGAN: Multi-source Domain Adaptation for Semantic Segmentation of Very High Resolution Satellite Images by Data Standardization.
Onur Tasar, Yuliya Tarabalka, Alain Giros, Pierre Alliez, Sebastien Clerc.
IEEE/CVF Conference on Computer Vision and Pattern Recognition EarthVision Workshop (CVPRW) Seattle, USA, 2020. Best paper award.

Abstract : Domain adaptation for semantic segmentation has recently been actively studied to increase the generalization capabilities of deep learning models. The vast majority of the domain adaptation methods tackle single-source case, where the model trained on a single source domain is adapted to a target domain. However, these methods have limited practical real world applications, since usually one has multiple source domains with different data distributions. In this work, we deal with the multi-source domain adaptation problem. Our method, namely StandardGAN, standardizes each source and target domains so that all the data have similar data distributions. We then use the standardized source domains to train a classifier and segment the standardized target domain. We conduct extensive experiments on two remote sensing data sets, in which the first one consists of multiple cities from a single country, and the other one contains multiple cities from different countries. Our experimental results show that the standardized data generated by StandardGAN allow the classifiers to generate significantly better segmentation.
Cost-driven framework for progressive compression of textured meshes. Cédric Portaneri, Pierre Alliez, Michael Hemmer, Lukas Birklein, Elmar Schoemer. 10th ACM Multimedia Systems Conference, 2019. Best paper award.

Abstract: Recent advances in digitization of geometry and radiometry generate in routine massive amounts of surface meshes with texture or color attributes. This large amount of data can be compressed using a progressive approach which provides at decoding low complexity levels of details (LoDs) that are continuously refined until retrieving the original model. The goal of such a progressive mesh compression algorithm is to improve the overall quality of the transmission for the user, by optimizing the rate-distortion trade-off. In this paper, we introduce a novel meaningful measure for the cost of a progressive transmission of a textured mesh by observing that the rate-distortion curve is in fact a staircase, which enables an effective comparison and optimization of progressive transmissions in the first place. We contribute a novel generic framework which utilizes the cost function to encode triangle surface meshes via multiplexing several geometry reduction steps (mesh decimation via half-edge or full-edge collapse operators, xyz quantization reduction and uv quantization reduction). This framework can also deal with textures by multiplexing an additional texture reduction step. We also design a texture atlas that enables us to preserve texture seams during decimation while not impairing the quality of resulting LODs. For encoding the inverse mesh decimation steps we further contribute a significant improvement over the state-of-the-art in terms of rate-distortion performance and yields a compression-rate of 22:1, on average. Finally, we propose a unique single-rate alternative solution using a selection scheme of a subset among LODs, optimized for our cost function, and provided with our atlas that enables interleaved progressive texture refinements.

Selective Padding for Polycube-Based Hexahedral Meshing. G. Cherchi, Pierre Alliez, R. Scateni, M. Lyon, D. Bommes.  Computer Graphics Forum, Wiley, 2019.

Abstract : Hexahedral meshes generated from polycube mapping often exhibit a low number of singularities but also poor quality elements located near the surface. It is thus necessary to improve the overall mesh quality, in terms of the minimum Scaled Jacobian (MSJ) or average Scaled Jacobian (ASJ). Improving the quality may be obtained via global padding (or pillowing), which pushes the singularities inside by adding an extra layer of hexahedra on the entire domain boundary. Such a global padding operation suffers from a large increase of complexity, with unnecessary hexahedra added. In addition, the quality of elements near the boundary may decrease. We propose a novel optimization method which inserts sheets of hexahedra so as to perform selective padding, where it is most needed for improving the mesh quality. A sheet can pad part of the domain boundary, traverse the domain and form singularities. Our global formulation, based on solving a binary problem, enables us to control the balance between quality improvement, increase of complexity and number of singularities. We show in a series of experiments that our approach increases the MSJ value and preserves (or even improves) the ASJ, while adding fewer hexahedra than global padding.

Curved Optimal Delaunay Triangulation
Leman Feng, Pierre Alliez, Laurent Busé, Hervé Delingette, and Mathieu Desbrun.ACM Transactions on Graphics (SIGGRAPH), 37(4), Art. 61, 2018.
Abstract: Meshes with curvilinear elements hold the appealing promise of enhanced geometric flexibility and higher-order numerical accuracy compared to their commonly-used straight-edge counterparts. However, the generation of curved meshes remains a computationally expensive endeavor with current meshing approaches: high-order parametric elements are notoriously difficult to conform to a given boundary geometry, and enforcing a smooth and non-degenerate Jacobian everywhere brings additional numerical difficulties to the meshing of complex domains. In this paper, we propose an extension of Optimal Delaunay Triangulations (ODT) to curved and graded isotropic meshes. By exploiting a continuum mechanics interpretation of ODT instead of the usual approximation theoretical foundations, we formulate a very robust geometry and topology optimization of Bézier meshes based on a new simple functional promoting isotropic and uniform Jacobians throughout the domain. We demonstrate that our resulting curved meshes can adapt to complex domains with high precision even for a small count of elements thanks to the added flexibility afforded by more control points and higher order basis functions.
Variance-Minimizing Transport Plans for Inter-surface Mapping

Manish Mandad, David Cohen-Steiner, Leif Kobbelt, Pierre Alliez and Mathieu Desbrun.

ACM Transactions on Graphics (SIGGRAPH), 2017.

See also Supplemental Material.

Abstract: We introduce an efficient computational method for generating dense and low distortion maps between two arbitrary surfaces of same genus. Instead of relying on semantic correspondences or surface parameterization, we directly optimize a variance-minimizing transport plan between two input surfaces that defines an as-conformal-as-possible inter-surface map satisfying a user-prescribed bound on area distortion. The transport plan is computed via two alternating convex optimizations, and is shown to minimize a generalized Dirichlet energy of both the map and its inverse. Computational efficiency is achieved through a coarse-to-fine approach in diffusion geometry, with Sinkhorn iterations modified to enforce bounded area distortion. The resulting inter-surface mapping algorithm applies to arbitrary shapes robustly, with little to no user interaction.

Students / post-docs / engineers
– 2020: Paul-Vinh Lê (intern, Ecole des Ponts ParisTech)
– 2020: Lucas Dubouchet (geometry compression)
– 2019: Tong Zhao (PhD student, 3IA Côte d’Azur)
– 2018: Julien Vuillamy (PhD student, Dassault Systèmes)
– 2018: Vasudha Varadarajan (intern from India, on binary reconstruction)
– 2018: Tong Zhao (intern from Ecole des Ponts, on geometric descriptors and spectral reconstruction)
– 2018: Vincent Vadez (Cifre PhD student on simplification of satellites, with Dorea Technology)
– 2018: Flora Quilichini (PhD student on mesh compression)
– 2018: Fernando Ireta (post-doc on indoor localization and reconstruction)
– 2017: Onur Tasar (PhD student on semantic classification of satellite images)
– 2017: Leman Feng (intern from Ecole des Ponts on Higher order meshes)
– 2017: Vinay Datta Renigunta (Efficient solver for optimal transportation)
– 2017: Dmitry Anisimov (LOD reconstruction of urban scenes)
– 2017: Cédric Portaneri (Geometry compression)
– 2016: Come Le Breton (Mesh generation)
– 2015: Guillaume Matheron (intern from ENS Paris on optimal transportation)
– 2015: Maxim Torgonskiy (Mesh generation)
– 2015: Aditya Kusupati (IIT Bombay on anisotropic metrics)
– 2015; Mohammad Rouhani (post-doc on semantic classification)
– 2015: Emmanuel Maggiori (PhD student on classification of satellite images)
– 2015: Nicolas Douillet (culture 3D clouds)
– 2014: Jinjing Shen (visiting PhD student on isotropic meshing of NURBS surfaces)
– 2014: Devdeep Ray (intern on optimal transportation)
– 2014: Henrik Zimmer (post-doc)
– 2013: Renata Rego (post-doc on Robust feature extraction)
– 2013: Anmol Garg (Intern on Shape approximation)
– 2012: Kaimo Hu (post-doc on Robust surface remeshing)
– 2012: Thijs van Lankveld (Surface reconstruction for cultural heritage data)
– 2012: Clément Jamin (Parallel algorithms and shape detection)
– 2012: Yiyi Wei (Well-centered triangulations, co-advised with Mariette Yvinec)
– 2012: Manish Mandad (PhD on robust shape approximation with guarantees)
– 2012: Sven Oesau (Indoor scene reconstruction, co-advised with Florent Lafarge)
– 2012: David Bommes (Surface tiling)
– 2011: Xavier Rolland-Neviere (Watermarking of surface meshes, at Technicolor, co-advised with Gwenael Doerr)
– 2011: Simon Giraudot (Robust reconstruction of surfaces)
– 2011: Paul Seron (Reconstruction of urban scenes)
– 2011: Renata Nascimento (visiting PhD student on quadrangle surface tiling)
– 2011: Julie Digne (post-doc on robust shape reconstruction, now researcher at CNRS in Lyon)
– 2011: Sagar Chordia (shape approximation)
– 2010: Alain Tayeb (Meshing NURBS surfaces)
– 2010: Boris Dalstein (quadrangle surface tiling)
– 2009-present: Bertrand Pellenard (PhD on surface and domain tiling, defended Dec 18th 2012)
– 2009: Hugo Feree (ENS Lyon: probing implicit surfaces, now PhD student at Inria Nancy)
– 2009: Rahul Srinivasan (IIT Bombay: accelerating ODT mesh optimization and sliver removal)
– 2008: Amit Gupta (IIT Bombay: Poisson reconstruction for polygon soups)
– 2008: Saurabh Chakradeo (IIT Bombay: Fast intersections and projections for polyhedral surfaces)
– 2007: Ankit Gupta (IIT Bombay: PCA in CGAL and application to normal estimation), now at Stanford
– 2006-2009: Jane Tournois (PhD on mesh optimization), now at Geometry Factory.
– 2006: Lakulish Antani (IIT Bombay: mesh sizing using additively weighted Voronoi diagrams), now at UNC
– 2004: Abdelkrim Mebarki (master: placement of streamlines)
– 2004: Jérôme Gahide (progressive triangle mesh compression)
– 2003-2007: Marie Samozino (Ph.D.: reconstruction of surfaces from noisy point sets, co-advised with Mariette Yvinec), now Professor in Mathematics
– 2002: Mathieu Monnier (compression of 2D vectorial data)

Ecole des Ponts ParisTech
MASTER EPU Ingénierie 3D and Interpolation 3D


I am an avid user of the CGAL library. I am a CGAL editor and developer as well, implementing or participating to various projects: placement of streamlines from 2D vector fields, planar parameterization of triangle surface meshes, Principal Component Analysis, Surface reconstruction, Point Set Processing and 3D Isotropic Tetrahedron Mesh Generation and Optimization.

Current Projects
– EU ITN GRAPES (Learning, processing and optimising shapes)
– EU BIM2TWIN (digital twin for construction)
– ANR Pisco (geometry compression)
– ANR Loca-3D (indoor localization and mapping)
– Google X (geometry processing)
Past Projects
– ERC Proof of Concept TITANIUM
– Google Chrome University research program
EU ERC Starting grant IRON (Robust Geometry Processing)
Grand emprunt Investissements d’avenir: Culture 3D clouds
(national project about geometric inference and analysis)
ANR GYROVIZ (national project for reconstructing urban scenes from localized photos and videos)
Focus K3D (EU FP7 Coordination Action)
AIM@SHAPE (EU Network of Excellence)
– Chair, EUROGRAPHICS PhD award committee
– Advisory committee: EUROGRAPHICS annual conference
– EUROGRAPHICS PhD award committee
– SGP 2020 Software and Dataset Awards Committee
– Thesis reviewer: Adrien Poulenard (Ecole Polytechnique)
– Thesis reviewer: Shayan Nikoohemat (University Twente)
– Thesis commitee: Jean Feydy (ENS Cachan)
– Thesis committee: Simon Rodgriguez (Inria)

– Full paper co-chair, EUROGRAPHICS conference.
Program co-chair, SPM conference.
– HDR reviewer: Sébastien Valette
– Thesis committee: Jean-Philippe Bauchet

– joined editorial board of Computer Graphics Forum for three years.
– programme committee: EUROGRAPHICS Symposium on Geometry Processing
– programme committee: International Conference on Geometric Modeling and Processing (GMP)
– programme committee: Shape Modeling International
– advisory committee: EUROGRAPHICS annual conference
– HDR committee: Stefanie Wuhrer (Inria Grenoble)
– Thesis committee: Arnaud Bletterer (I3S Sophia Antipolis)
joined the SMA Executive Board
– programme committee: ACM SIGGRAPH 2017
– programme committee: EUROGRAPHICS 2017
– programme committee: EUROGRAPHICS Star reports
– programme committee: EUROGRAPHICS Symposium on Geometry Processing
– programme committee: EG Workshop on Graphics and Cultural Heritage
– thesis reviewer: Giorgio Marcias (CNR Pisa, Italy)
– thesis reviewer: Claudio Calabrese (University Roma, Italy)
– thesis reviewer: Florian Caillaud (LIRIS Lyon)
– thesis reviewer: Dmitry Anisimov (Univ. Lugano)
– thesis reviewer: Yannick Masson (University Paris Est)
– thesis reviewer: Ana Vintescu (Telecom ParisTech)
– HDR committee: Maks Ovsjanikov (Ecole Polytechnique)

– programme committee: ACM SIGGRAPH 2016
– programme committee: EUROGRAPHICS 2016
– programme committee: Geometric Modeling and Processing 2016
– programme committee: Shape Modeling International 2016
– programme committee: EUROGRAPHICS Symposium on Geometry Processing
– programme committee: EUROGRAPHICS Workshop on Graphics & Cultural Heritage
– thesis reviewer: Ludovic Blache (CReSTIC-SIC Reims-Châlons-Charleville)
– thesis reviewer: Ruqi Huang (Inria Saclay)
– thesis reviewer: Li Wang (Inria Grenoble)
– thesis comittee: Mael Rouxel-Labbé (Inria)

– thesis reviewer: Jérémy Levallois (LIRIS)
– thesis committe: Rodolphe Vaillant (Université Paul Sabatier / University of Victoria)
– paper committee, EUROGRAPHICS Symposium on Geometry Processing (Graz, Austria)
– programme committee, Digital Heritage 2015
– thesis reviewer: Gilles-Philippe Paillé (Université de Montréal)

– thesis reviewer: Louis Cuel (Université de Savoie)
– thesis committee: Jean luc Peyrot (CNRS-Université de Nice)
thesis reviewer: Alexandre Boul’ch (Ecole des Ponts ParisTech)
– Joined Horizon 2020 Advisory Group for Societal Challenge 6 ‘Europe in a changing world – Inclusive, Innovative and Reflective Societies.
– European paper co-chair, Geometric Modeling and Processing (Singapore)
– program committee, International Conference on 3D Computer Vision
– program committee, Shape Modeling International
thesis reviewer: Ricard Campos (University of Girona)
– joined the Steering Board of the EUROGRAPHICS Workshop on Graphics and Cultural Heritage
thesis reviewer: Henrik Zimmer (University of Aachen)
– program committe, EUROGRAPHICS Workshop on Graphics and Cultural Heritage
– paper committe, EUROGRAPHICS Workshop on Urban Data Modelling and Visualisation
– paper committee, EUROGRAPHICS Symposium on Geometry Processing (Cardiff, UK)
– thesis reviewer: Thierry Guillemot  (Telecom ParisTech)

paper committee, ACM Virtual Reality International Conference
– local board member for Digital Heritage 2013
– thesis committee: Ricardo Uribe-Lobello (LIRIS, CNRS Lyon)
– thesis committee: Yannick Verdie (Inria)
– thesis reviewer: Thijs van Lankveld (Utrecht)
– thesis committee: Yannick Verdie (Inria)
– thesis committee: Adrien Maglo (Centrale Paris)
– thesis committee: Noura Faraj (Telecom ParisTech)
– joined board of Computer Aided Geometric Design
– paper committee, Shape Modeling International 2013
– paper committee, Eurographics Symposium on Geometry Processing (Genova, Italy)
– HDR thesis reviewer: Guillaume Lavoue (Universite de Lyon)

– thesis reviewer, Nicolas Mellado, (Inria Bordeaux)
– thesis reviewer, David Bommes (RWTCH Aachen)
– invited speaker, MICCAI workshop on Mesh Processing in Medical Image Analysis (Nice).
– invited speaker, 3DIMPVT: 3D Imaging, Modeling, Processing, Visualization and Transmission (Zurich).
– paper committee, EUROGRAPHICS conference (Cagliari, Italy)
– paper committee, Eurographics Symposium on Geometry Processing (Talinn, Estonia)
– program committee, International Workshop on Point Cloud Processing (in conjunction with CVPR)
– invited speaker, Advances in Architectural Geometry (Paris).

– thesis reviewer: Vincent Vidal (Universite de Lyon)
– HDR thesis reviewer: Raphaelle Chaine (Universite de Lyon)
– thesis committee: Patrick Mullen (Caltech)
– programme committee, VAST International Symposium on Virtual Reality, Archaeology and Cultural Heritage
programme committee, Sibgrapi 2011
– paper committee, Eurographics Symposium on Geometry Processing
– programme committee, Shape Modeling International
– thesis reviewer: Clement Courbet (Ecole Centrale Paris)
– thesis committee: Marcio Cabral (INRIA Sophia)
– thesis reviewer: Sahar Hassan (University of Grenoble)

– joined board of Elsevier Graphical Models
– thesis reviewer: Julie Digne (ENS Cachan)
paper co-chair, Pacific Graphics 2010
– programme committee, Shape Modeling International
programme committee, ACM Symposium on Solid and Physical Modeling
– paper committee, Eurographics Symposium on Geometry Processing
– scientific committee: Advances in Architectural Geometry
– thesis committee: Mathieu Bredif (Telecom ParisTech and IGN, France)
– thesis reviewer: Thierry Stein (INRIA Rhone Alpes)

– associate editor of the ACM Transactions on Graphics
short paper co-chair, Eurographics
programme committee, IMA Mathematics of Surfaces XIII conference.
– programme committee, SIAM/ACM Joint Conference on Geometric and Physical Modeling
– paper committee, Eurographics Symposium on Geometry Processing
– paper committee, Pacific Graphics
– thesis reviewer: Patrick Labatut (ENS Paris)
– thesis committee: Jean-Marie Favreau (University of Clermont-Ferrand)
– thesis committee: Jane Tournois (INRIA Sophia)

paper co-chair, Eurographics Symposium on Geometry Processing
– paper committee, EUROGRAPHICS
– paper committee, Pacific Graphics
– paper committee, Shape Modeling International
– paper committee, ACm Symposium on Solid and Physical Modeling
– paper committee, Symposium on 3D Data Processing, Visualization and Transmission
– thesis reviewer: Christopher Dyken (University of Oslo)
– thesis reviewer: Johan Seland (University of Oslo)

– paper committee, SIGGRAPH
– paper committee, CAD/Graphics
– paper committee, Pacific Graphics
– paper committee, Shape Modeling International
– paper committee, ACM Symposium on Solid and Physical Modeling
– paper committee, Eurographics Symposium on Geometry Processing

paper committee, Pacific Graphics
– associate editor of the Visual Computer
– associate editor of Computers & Graphics
– part of the french ANR project GEOTOPAL
– thesis reviewer: Martin Marinov (RWTH Aachen)
– paper committee, ACM Symposium on Solid and Physical Modeling
paper committee, Eurographics Symposium on Geometry Processing
– paper committee, IEEE International Conference on Shape Modeling and Applications

– Video and Multimedia presentation program committee, SOCG 2005
– paper committee, EUROGRAPHICS Symposium on Geometry Processing 2005
– paper committee, EUROGRAPHICS 2005
– paper committee, Pacific Graphics 2005
– thesis reviewer: Christian Rossl (MPII Saarbruck), Raphaele Balter (University of Rennes)
– member of thesis committee:Marie-Claude Frasson (University of Nice), Guillaume Lavoue (University of Lyon), Gabriel Peyre (Ecole Polytechnique)

– ACI GeoComp 2004-2007
AIM@SHAPE EU Network of Excellence (workpackage leader)

– organizing co-chair, Second Eurographics Symposium on Geometry Processing 2004
– paper committee, Eurographics Symposium on Geometry Processing 2004
– paper committee, Eurographics 2004
– paper committee, Pacific Graphics 2004
– paper committee, Shape Modeling International 2004
– member of thesis committee: Frederic Payan


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