I am a data scientist at the Boston Consulting Group (BCG), in the new practice Gamma. I have been researcher and professor for 15 years at the Mathematics department, PUC - Rio de Janeiro. I was working on different domains of Applied Mathematics: from Computational Geometry and Topology to Computer Graphics, from discrete Morse theory to Geometry Processing, from Reservoir Modeling to Computational Fluid Dynamics.

I have been elected affiliated member of the Brazilian Academy of Sciences for 2012/2016. I have also been invited as keynote speaker at the TopoInVis 2011 workshop (talk slides, also available in pdf). I organized with Esteban Clua the Sibgrapi 2009 at PUC and ACM SoCG 2013 with Luis Peñaranda. I have been, with Ricardo Torres, program chair of the Sibgrapi 2011. I am also editor of the following journals: Computer Graphics Forum, Image Processing On Line and Anais da Academia Brasileira de Ciências.

I participated during my post-doctoral period to the Discrete Differential Geometry Group of Freie Universität Berlin, under the supervision of Konrad Polthier, the Computer Graphics Group of Tel Aviv University, under the supervision of Daniel Cohen-Or, and the Discrete Geometry Group of Technische Universität Berlin, under the supervision of Günter Ziegler.

I received a PhD in Computer Science from the Université Paris VI on *Mesh Compression from Geometry*, advised by Professor Jean-Daniel Boissonnat of the Géométrica Project (PRISME) at the INRIA - Sophia Antipolis,
and another PhD in Mathematics from PUC - Rio de Janeiro on *Geometric Discrete Morse Complexes*, advised by Professor Hélio Lopes, of the Department of Mathematics.
There, I also obtained my M.Sc. degree in Mathematics on *Constructing Discrete Morse Functions*, at PUC - Rio de Janeiro, which also validated my diplomas from the Telecom ParisTech and thus for the École Polytechnique too.

## Selected publications

Hover the mouse over an image to access the corresponding publication. A complete list of publications is available here.**Selected for publication from the Sibgrapi 2013 conference**

This work introduces a topological graph construction based on streamlines. It is guaranteed to produce a coherent result even when some singularities are not detected. This work also details an application of topological graphs to improve the generation of self-animated images. In this application, the streamline-based approach carries almost no overhead, since self-animated images already rely on streamlines, but leads to a threefold speed-up of the core processing..

**Selected for publication in Pattern Recognition Letters**

Thanks to The Visual Computer’s editor in chief Nadia Magnenat-Thalmann, this issue presents eight papers selected from a pool of 46 papers presented during the technical sessions of the conference. They represent the main topics inside visual computing, from computational topology and modeling to rendering, visualization, and simulation.

Special issue on

**Foundations of Topological Analysis**

We also paid a lot of attention to the technical papers this year, significantly increasing the number of international committee members, improving the review process, and reforming the selection criteria to better cope with the diversity of areas of Sibgrapi. We received 123 submissions in the first phase, a significant increase compared to previous year. It should be mentioned that the overall quality of submissions was very good this year. During the double blind review process, we achieved motivating several discussions between the 176 referees and, after the disclosing of the reviews, with the authors. We discussed the acceptance of each paper with the reviewers and, for almost all papers, achieved a unanimous decision, leading to 46 technical papers accepted for presentation during the event.

The richness of the technical papers can be mainly credited to the authors, who have chosen Sibgrapi to submit their work, and to the reviewers, who dedicated a lot of their valuable time in the revision, discussion and final approval period. We also would like to thank the local organization committee, the several committees in charge of the different technical activities, the invited speakers, the session chairs, and the tutorial instructors. Finally, we are grateful to several institutions which were involved directly or indirectly in the organization of Sibgrapi 2011: Universidade Federal de Alagoas (UFAL), Pontifícia Universidade Católica do Rio de Janeiro (PUC-Rio), Universidade Estadual de Campinas (Unicamp), and the Brazilian Computer Society (SBC).

**Selected for publication from the Sibgrapi 2010 conference**

**Selected for publication in The Visual Computer**

**Extended version of the Sibgrapi 2008 conference**.

**Selected for publication from the SoCG 2008 conference**

**Extended in Journal of Mathematical Imaging and Vision.**

**Selected for publication in Discrete and Computational Geometry**

**Selected for publication from the Sibgrapi 2006 conference**Check also the technical report Convergence of affine estimators on parabolic polygons.

**Selected for publication from the Sibgrapi 2005 conference**

**Extended in Computer-Aided Design.**

**Selected for publication in the Journal of Mathematical Imaging and Vision**

**Selected for publication from the Sibgrapi 2004 conference**

directed by Jean--Daniel Boissonnat

**Selected for publication in Computer Graphics Forum**

Check also the technical report CHE: A scalable topological data structure for triangular meshes.

**Selected for publication from the Sibgrapi 2004 conference**. Check also the technical report Least Squares Estimation of Curvature and Torsion.

**Selected for publication from the Sibgrapi 2003 conference**

**Selected for publication in Computers & Graphics**

**Selected for publication in Computerized Medical Imaging and Graphics**

**Selected for publication from the Visualization and Mathematics 2002 conference**

**Selected for publication in Computer Graphics Forum**

(also available in Portuguese, and in a short version presented at the Sibgrapi 2003 WTD)

**Selected for publication in IEEE TVCG**

## Projects

- FAPERJ - Young Scientist of Rio (2016-2019): Gesture and signs recognition.
- FAPERJ - Scientific Initiation (2013-2014): Scholarship for Anna Lívia Souza on Seismic Measures within Ocean Waves.
- CAPES - PAEP, FAPERJ - APQ2, INCT Mat, CNPq - ARC and Springer: sponsoring for SocG 2013.
- FAPERJ - Young Scientist of Rio (2012-2015): Research project on discrete geometry and topology.
- FAPERJ - PhD internship abroad (2012.2): Support for the internship of João Paixã at The University of Queensland (Australia), under the supervision of Benjamin Burton.
- FAPERJ - PhD internship abroad (2012.1): Support for the internship of Renata Nascimento at INRIA (France), under the supervision of Pierre Alliez.
- Scholarship for CNPq researchers - level 1D (2011-2014): Research project on discrete geometric modeling.
- MCT/CNPq - Universal (coordinator) (2010-2011): Research project on evolving discrete surfaces.
- CNPq - Master scholarship (2009-2011): Master scholarship on implicit surfaces and visualization.
- CNPq - ARC, CAPES - PAEP, Petrobras, FAPERJ - APQ2, INCT Mat, PUC-Rio and UFF: sponsoring for Sibgrapi 2009.
- FAPERJ - Young Scientist of Rio (2009-2012): Research project on reconstruction of geometric objects.
- ARCUS (2008-2010): International collaboration project between the Rhône-Alpes region and Brazil, within the Joseph Fourier Grenoble University and PUC-Rio.
- Scholarship for CNPq researchers - level 2 (2008-2010): Research project on 3D reconstruction.
- MCT/CNPq - Universal (2008-2009): Research project on stochastic dynamic and geometry of point objects with applications to geological faults.
- FAPERJ - Think Rio (2008-2009): ModFin research project for software development of a modeling, simulation and generation of financial and macro-economical scenarios, with applications to ALM systems.
- MCT/CNPq - Universal (coordinator) (2007-2008): Research project on 3D objects compression from the combinatorial and geometrical point of view.
- MCT/CNPq - Universal (2007-2008): Research project on Euclidean, affine and projective geometry of discrete curves.
- INRIA / CNPq (2005-2008): International collaboration project between the Mathematics department of PUC-Rio and the Géométrica Project of the INRIA-Sophia Antipolis.

- Dynamics of salt diapir (since 2011) - Petrobras (petróleo): analysis, numerical simulations and visualisation of salt thermo-mechanical states.
- Turbidites Lobes (2006-2010) - Petrobras (oil & gas): multiphase fluid simulation.
- KernelSis (2007-2009) - Petrobras (oil & gas): joint learning of seismic and well data.
- MultiFacsis (2007-2008) - Petrobras (oil & gas): analysis and visualization of seismic data with multi-attributes.
- Pigalyse (2007-2008) - CPTI (instrumentation):: reconstruction from diagonally-oriented ultrasound rays.
- Petbool (2007) - Petrobras (oil & gas): stochastic geologic reservoir modeling.
- Geosis (2004-2008) - Petrobras (oil & gas): multiattribute reconstruction of seismic data.
- Poros (August-December 2003) - Petrobras (oil & gas): porous sediments simulator.
- SiniPrev (July-August 2002) - Bradesco Insurance (insurance): analysis method for sinister occurrence.
- Geosis (August-September 2002) - Petrobras (oil & gas): surface reconstruction algorithm from seismic data.
- Sirrocco (February-June 2001) - Telecom ParisTech (telecommunications): perfect hashing algorithm for dictionary structuring.

## Colleagues

- Álvaro Veiga: Department of Electrical Engineering, PUC-Rio.
- Adelailson Peixoto: Department of Mathematics, Federal University of Alagoas.
- Afonso Paiva Neto: ICMC, USP - São Carlos.
- Alex Laier Bordignon: Department of Mathematics, PUC-Rio.
- Alla Sheffer: Computer Science Department, UBC.
- Allyson Cabral: Department of Mathematics, PUC-Rio:
*PhD student*. - Americo Barbosa da Cunha Junior: Department of Mechanical Engineering, PUC-Rio:
*Undergraduate final project student*. - Andrei Sharf: Computer Science Department, Ben-Gurion University.
- Anna Lívia Souza: CEFET - RJ:
*Scientific initiation student (PICME)*. - Antônio Wilson Vieira: Unimontes.
- Antonio Claudio Soares: CENPES, Petrobras.
- Ariel Shamir: School of Computer Science, The Interdisciplinary Center of Herzliya.
- Armando Prestes: SINTEF Brasil.
- Arthur Kölblinger: CEFET - RJ:
*Scientific initiation student (PICME)*. - Benjamin A. Burton: School of Mathematics and Physics, the University of Queensland.
- Bernardo Ribeiro: Dom Pedro II high school:
*Scientific initiation student*. - Betina Vath: Department of Petroleum Engineering, UFF:
*Master student (dissertation)*. - Bianca Lodoli: IME:
*Scientific initiation student (PICME)*. - Carlos Simonsen Leal: Department of Mathematics, UFRJ:
*Scientific initiation student*. - Catiuscia Borges: School of the Jockey Club Brasileiro:
*Master student (dissertation)*. - Chen Greif: Computer Science Department, UBC.
- Clarissa Codá Marques: Department of Mathematics, PUC-Rio:
*PhD student (thesis)*. - Cynthia Oliveira Lage Ferreira: ICMC, USP - São Carlos.
- Dan Alcantara: Department of Computer Science, UC Davis.
- Daniel Cohen-Or: School of Computer Science, Tel Aviv University.
- Daniel Fleischman: Cornell University:
*Undergraduate final project student*. - David Cohen-Steiner: Géométrica Project, INRIA - Sophia Antipolis.
- David Rey: LICIT, INRETS:
*Master student (dissertation)*. - Dimas Martinez Morera: Department of Mathematics, Federal University of Alagoas.
- Eliton Filho: IME:
*Scientific initiation student (PICME)*. - Eric Cardona Romani: Department of Physics, PUC-Rio:
*Undergraduate final project student*. - Eric Fusy: LIX, Ecole Polytechnique.
- Erick Costa e Silva Talarico: Petrobras:
*Scientific initiation student*. - Esdras Medeiros: Department of Mathematics, Federal University of Ceará.
- Esteban Clua: Computer Science Department, UFF.
- Fabiano Petronetto do Carmo: Department of Mathematics, Federal University of Espírito Santo.
- Frédéric Cazals: ABS Project, INRIA - Sophia Antipolis.
- Frédéric Chazal: Géométrica Project, INRIA - Saclay.
- Günter Ziegler: Matheon Project, Technische Universität Berlin.
- Geovan Tavares: Department of Mathematics, PUC-Rio.
- Gil Shklarski: Microsoft Redmond.
- Guilherme Dias da Fonseca: .
- Hélio Lopes: Department of Mathematics, PUC-Rio:
*Master and PhD advisor*. - Henri Anciaux: Institute of Mathematics ans Statistics, USP.
- I-Shih Liu: Mathematics Institute, UFRJ.
- Jarek Rossignac: College of Computing, Georgia Tech.
- Jean-Daniel Boissonnat: Géométrica Project, INRIA - Sophia Antipolis:
*PhD advisor*. - Jean-Marie Morvan: Camille Jordan Institute, Claude Bernard University of Lyon.
- João Domingos Gomes: .
- João Luiz Campos: TecGraf, PUC-Rio.
- João Paixão: Department of Computer Sciences, UFRJ:
*Master (dissertation) and PhD student*. - Jonathan Spreer: School of Mathematics and Physics, the University of Queensland.
- Jyrko Correa Morris: Department of Mathematics, PUC-Rio:
*PhD student (thesis)*. - Karen Carilho: Department of Mathematics, PUC-Rio:
*PhD student*. - Karine Pereira: Department of Mathematics, PUC-Rio:
*Master student*. - Konrad Polthier: Matheon Project, Freie Universität Berlin.
- Leandro Lopes: IME:
*Scientific initiation student (PICME)*. - Leandro Miranda: Department of Mathematics, Federal University of Alagoas.
- Leif Kobbelt: Computer Science Department, RWTH Aachen.
- Lis Custódio: Department of Mathematics, PUC-Rio:
*Master student (dissertation)*. - Luca Castelli Aleardi: LIX, Ecole Polytechnique.
- Lucas Mauricio Sigaud: Department of Physics, PUC-Rio.
- Lucas von Haehling Braune: Department of Mathematics, PUC-Rio:
*Scientific initiation student (report)*. - Luis Peñaranda: Department of Computer Sciences, UFRJ.
- Luiz Henrique de Figueiredo: VISGRAF Laboratory, IMPA.
- Luiz Palermo: CENPES, Petrobras.
- Luiz Velho: VISGRAF Laboratory, IMPA.
- Mário Fernando Montenegro Campos: Department of Computer Sciences, UFMG.
- Marcelo Dreux: Department of Mechanical Engineering, PUC-Rio.
- Marcos Craizer: Department of Mathematics, PUC-Rio.
- Marcos Oliveira Lage Ferreira: Department of Informatics, UFF.
- Maria de Andrade: Department of Mathematics, Federal University of Alagoas:
*PhD student (thesis)*. - Mariana Milazzo: Dom Pedro II high school:
*Scientific initiation student*. - Marina Dias: Department of Mathematics, PUC-Rio.
- Mario Fernando Montenegro Campos: Department of Computer Sciences, UFMG.
- Matheus Felipe Ferreira Maciel: Department of Computer Science, PUC-Rio:
*Scientific initiation student*. - Mauro Antonio Rincon: Mathematics Institute, UFRJ.
- Moacyr Alvim Barbosa: Getulio Vargas Foundation.
- Nina Amenta: Department of Computer Science, UC Davis.
- Paulo Paraizo: CENPES, Petrobras.
- Pierre Alliez: Géométrica Project, INRIA - Sophia Antipolis.
- Rafael Cação: IME:
*Scientific initiation student (PICME)*. - Rafael Lassance de Oliveira Alonso Martinez: Department of Mathematics, PUC-Rio:
*Scientific initiation and master student*. - Raffael Capano de Arruda: Department of Computer Science, PUC-Rio:
*Scientific initiation student*. - Ralph Costa Teixeira: Mathematics Institute, UFF.
- Renata Nascimento: Department of Mathematics, PUC-Rio:
*Master (dissertation) and PhD student*. - Renato Paes Leme: Google Research New York.
- Rener Pereira de Castro: Itaú Bank:
*PhD student (thesis)*. - Ricardo da Silva Torres: Institute of Computing, Unicamp.
- Rodrigo de Toledo: Department of Computer Sciences, UFRJ.
- Rogério Santos: International, Petrobras.
- Roger Véron: Department of Mathematics, PUC-Rio:
*PhD student*. - Rolci Cipolatti: Mathematics Institute, UFRJ.
- Romulo Brito: Department of Computation, UFRJ:
*Master student (dissertation)*. - Scarlett de Botton: .
- Sinésio Pesco: Department of Mathematics, PUC-Rio.
- Sivan Toledo: School of Computer Science, Tel Aviv University.
- Thales Vieira: Department of Mathematics, Federal University of Alagoas:
*Master (dissertation) and PhD student (thesis)*. - Thiago Pereira: Princeton University.
- Victor Hugo de Oliveira: IME:
*Scientific initiation student (PICME)*. - Vinícius Mello: Department of Mathematics, Federal University of Bahia.
- Welles A.M. Morgado: Department of Physics, PUC-Rio.
- William Robson Schwartz: Department of Computer Sciences, UFMG.

## Teaching

- MAT2464 (2015.1): Introduction to computational topology (graduate course in Mathematics).
- MAT1200 (2015.1): Linear algebra, coordinator (undergraduate course in Mathematics).
- MAT1200 (2014.2): Linear algebra, coordinator (undergraduate course in Mathematics).
- MAT1305/MAT2462 (2014.2): Geometric modeling (under and graduate course in Mathematics).
- MAT1200 (2014.1): Linear algebra, coordinator (undergraduate course in Mathematics).
- MAT1231/MAT2229 (2014.1): Numerical linear algebra (under and graduate course in Mathematics).
- MAT1305/MAT2462 (2013.2): Geometric modeling (under and graduate course in Mathematics).
- MAT1310 (2013.2): Discrete Mathematics (undergraduate program of the School of Sciences).
- MAT2465 (2013.1): Discrete and computational geometry (graduate course in Mathematics).
- MAT1231/MAT2229 (2013.1): Numerical linear algebra (under and graduate course in Mathematics).
- MAT1406/MAT2447 (2012.2): Numerical methods for differential equations (graduate course in Mathematics).
- MAT1305/MAT2442 (2012.1): Geometric modeling (under and graduate course in Mathematics).
- MAT1301 (2012.1): Mathematical Fundaments for Computer Graphics (under and graduate course in Mathematics).
- MAT1231/MAT2229 (2012.1): Numerical linear algebra (under and graduate course in Mathematics).
- Topology of discrete manifolds (and non-manifolds) through cell complexes : mini-course lectured at the trimester program on Computational Manifolds and applications (IMPA).
- MAT1406/MAT2447 (2011.2): Numerical methods for differential equations (graduate course in Mathematics).
- MAT1310 (2011.2): Discrete Mathematics, coordinator (undergraduate program of the School of Sciences).
- Geometric invariant calculus and estimation: an introduction to Euclidean and affine geometries, with Maria Andrade (08/2011): Short course program of the 28
^{th}Brazilian Mathematics Colloquium at IMPA. - Mathematical Fundaments for Image Processing (2011.1): Introduction to image processing (under and graduate course in Mathematics).
- MAT1310 (2011.1): Discrete Mathematics, coordinator (undergraduate program of the School of Sciences).
- Implicit curves and surfaces: elements of differential and discrete geometries, with Maria Andrade, Allyson Cabral, Vinícius Mello and Adelailson Peixoto (03/2011): Short course program of the 1
^{st}Mathematics Colloquium of the North East. - Reconstruction (2010.2): 3D Reconstruction Methods (graduate course in Mathematics).
- MAT1310 (2010.2): Discrete Mathematics, coordinator (undergraduate program of the School of Sciences).
- Computational Topology (2010.1): introduction to algebraic and combinatorial topologies with their computational counterparts (graduate course in Mathematics).
- MAT1071 (2010.1): Lecture of Mathematics of Space and Shapes, using Google Sketch'Up, given to first grade student at the Department of Architecture and Urban Planning, PUC - Rio de Janeiro.
- MAT1305/MAT2442 (2009.2): Geometric modeling (under and graduate course in Mathematics).
- MAT1071 (2009.2): Lecture of Mathematics of Space and Shapes, given to first grade student at the Department of Architecture and Urban Planning, PUC - Rio de Janeiro.
- MAT1161 (2009.2): Calculus with one Variable, Maple class (undergraduate program of the School of Sciences).
- Meshless fluid simulation: an introduction to SPH methods, with Afonso Paiva, Fabiano Petronetto and Geovan Tavares (08/2009): Short course program of the 27
^{th}Brazilian Mathematics Colloquium at IMPA. - MAT1072 (2009.1): Lecture of Calculus, given to second year student at the Department of Architecture and Urban Planning, PUC - Rio de Janeiro.
- MAT1071 (2009.1): Lecture of Mathematics of Space and Shapes, given to first grade student at the Department of Architecture and Urban Planning, PUC - Rio de Janeiro.
- MAT1161 (2009.1): Calculus with one Variable, Maple class (undergraduate program of the School of Sciences).
- Introduction to Computer Graphics, with Vinícius Mello (01-02/2009): Lecture at the Summer School of the Federal University of Alagoas.
- Implicit Surfaces and Isosurfaces: from Calculus Course to Medical, Game and Oil Industries, with Adelailson Peixoto (11/2008): one week course offered at the IV National Symposium / Scientific Initiation Days at IMPA.
- Advanced modeling (2008.2): advances in geometric modeling from 1990 to 2008 (graduate course in Mathematics).
- MAT1153 (2008.2): Integral Calculus with Multiple Variables, coordinator (undergraduate program of the School of Sciences).
- MAT1153 (2008.1): Integral Calculus with Multiple Variables, coordinator (undergraduate program of the School of Sciences).
- Reconstruction (2007.2): 3D Reconstruction Methods (lectured with Luiz Velho and Dimas Martinez Morera at IMPA).
- 3D Compression: from A to Zip (10/2007): Tutorial given during the Sibgrapi 2007 conference.
- MAT1610/MAT2620 (2007.2): Real Analysis (graduate course in Mathematics).
- MAT1153m (2007.2): Integral Calculus with Multiple Variables with Maple (undergraduate program of the School of Sciences).
- MAT1301 (2007.1): Mathematical Fundaments for Computer Graphics (graduate course in Mathematics).
- MAT1151 (2007.1): Calculus with one Variable, Maple class (undergraduate program of the School of Sciences).
- MAT2413 (2006.2): Distribution theory (post-graduate course in Mathematics).
- MAT1172 (2006.2): Differential Calculus with Multiple Variables, special class (undergraduate program of the School of Sciences).
- 3D Objects Compression (06/2006): One week course at Matfest 2006, organized by the Federal University of Alagoas.
- MAT1153 (2006.1): Integral Calculus with Multiple Variables (undergraduate program of the School of Sciences).
- MI1 (2003.2): Monitoring practical works of computer science of first-year students of the Computer Science Department, Nice University.
- MAT1071 (2002.1): Lecture of Mathematics of Space and Shapes, given to first grade student at the Department of Architecture and Urban Planning, PUC - Rio de Janeiro.

## Downloads

- Shell script to create pdf and video teaser thumbnails using ImageMagick and FFmpeg: for pdfs, pdfthumb bash script (3 KB, modified on March 30th, 2012), and for video, videothumb bash script (3 KB, modified on July 9th, 2011).
*Open source*code for the Very Simple Volume Rendering algorithm: ZIP file (92 KB, modified on May 16th, 2010).- Simple LaTeX package for image insertion: ZIP file (2 KB, modified on March 7th, 2008).
- LaTeX format for the preprints of the Mathematic Department of PUC-Rio: ZIP file (580 KB, modified on February 19th, 2008).
- LaTeX format for PhD and Master thesis at PUC-Rio: ZIP file (619 KB, modified on August 22nd, 2011), in collaboration with Marcelo Roberto Jimenez.
*Open source*code for the paper on Marching Cubes, with examples: ZIP file (166 KB, modified on December 14th, 2009).- Demonstration program (windows) for the paper on Arc-Length Based Curvature Estimation, with examples: ZIP file (611 KB, modified on August 3rd, 2006).

## Contact

- Email: lewiner@gmail.com
- Home Page: thomas.lewiner.org