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Stylisation Temporellement Cohérente D'animations 3D Basée Sur Des Stylisation temporellement cohérente d’animations 3D basée sur des textures Pierre Bénard To cite this version: Pierre Bénard. Stylisation temporellement cohérente d’animations 3D basée sur des textures. Math- ématiques générales [math.GM]. Université de Grenoble, 2011. Français. NNT : 2011GRENM024. tel-00630112 HAL Id: tel-00630112 https://tel.archives-ouvertes.fr/tel-00630112 Submitted on 7 Oct 2011 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. THÈSE Pour obtenir le grade de DOCTEUR DE L’UNIVERSITÉ DE GRENOBLE Spécialité : Mathématiques et Informatique Arrêté ministériel : 7 août 2006 Présentée par Pierre Bénard Thèse dirigée par François Sillion et codirigée par Joëlle Thollot préparée au sein du Laboratoire Jean Kuntzmann dans l’École Doctorale Mathématiques, Sciences et Technologies de l’Information, Informatique Stylisation temporellement cohérente d’animations 3D basée sur des textures Temporally Coherent Stylization of 3D Animations based on Textures Thèse soutenue publiquement le 7 juillet 2011, devant le jury composé de : Marie-Paule Cani Professeur à l’université de Grenoble, Présidente Bernard Péroche Professeur à l’université Claude Bernard Lyon 1, Rapporteur Aaron Hertzmann Professeur associé à l’université de Toronto, Rapporteur Adam Finkelstein Professeur associé à l’université de Princeton, Examinateur François Sillion Directeur de Recherche à l’INRIA, Directeur de thèse Joëlle Thollot Professeur à l’université de Grenoble, Co-Directeur de thèse Pierre Bénard: Stylisation temporellement cohérente d’animations 3D basée sur des textures, Thèse de l’Université de Grenoble, © 7 juillet 2011 RÉSUMÉ Cette thèse s’inscrit dans le thème du rendu expressif qui vise à définir des outils de création et de traitement d’images ou d’animations stylisées. Les applications concernent tous les métiers nécessitant une représentation visuelle stylisée : créa- tion artistique (jeux vidéo, film d’animation, dessins animés), restitution archéolo- gique, documentation technique, etc. Outre les qualités et l’expressivité du style, un critère fondamental de qualité d’une image est l’absence d’artefacts visuels. Cette considération a toujours existé, mais elle est particulièrement importante dans le cas de l’informatique graphique. En effet, la nature même de l’image – des pixels discrets – est source d’artefacts. Les artefacts sont encore plus visibles lorsque l’on s’intéresse aux animations, des artefacts temporels s’ajoutant aux artefacts spatiaux. Définir précisément ces artefacts est complexe car certains imperfections d’un style peuvent aussi être désirables et faire partie de ses qualités. L’objectif de cette thèse est d’une part d’analyser et d’évaluer perceptuellement ces artefacts, et d’autre part de proposer de nouvelles méthodes de stylisation d’animations 3D temps-réel. Nous présentons tout d’abord un ensemble de techniques pour créer et assurer la cohérence de dessins au trait extraits de scènes 3D animées. Nous proposons ensuite deux méthodes de stylisation des régions de couleur permettant la créa- tions d’un grand nombre de motifs. Le point commun à toutes ces approches est la représentation du médium simulé (pigment d’aquarelle, coup de crayon ou de pinceau...) par une texture évoluant au cours de l’animation. Nous décrivons en- fin deux expériences utilisateurs visant à évaluer perceptuellement la qualité des résultats produits par ce type de techniques. Mots clés : Rendu Non-Photoréaliste, Cohérence Temporelle, Textures. iii ABSTRACT This PhD thesis deals with non-photorealistic rendering, a sub-field of computer graphics which aims at defining creation and processing tools to stylize images and animations. It has applications in all the fields that need stylized depictions, such as entertainment (e. g., video games, animated films, cartoons), virtual her- itage, technical illustration, etc. Besides quality and expression of style, a crucial criterion to assert the quality of an image is the absence of visual artifacts. While already true for traditional art, this consideration is especially important in computer graphics. Indeed the intrin- sic discrete nature of an image can lead to artifacts. This is even more noticeable during animations, as temporal artifacts are added to spatial ones. Precisely defin- ing these artifacts is complex as certain flaws of a given style may be part of its unique and desirable quality (e. g., the imperfections in a hand-made work). The goal of this thesis is twofold: (1) To analyse and perceptually evaluate these artifacts; (2) To propose new methods for stylizing real-time 3D animations. First we present a set of techniques to ensure the coherence of line drawings ex- tracted form 3D animated scenes. Then we propose two methods to stylize shaded regions, which allow to create a wide variety of patterns. The shared ground layer of all these approaches is the use of temporally varying textures to represent the simulated media (e. g., watercolor pigments, brush strokes). Finally we describe two user studies aiming at evaluating the quality of the results produced by such techniques. Keywords: Non-Photorealistic Rendering, Temporal Coherence, Textures. iv REMERCIEMENTS La thèse est une aventure certes personnelle mais jamais solitaire, j’aimerais donc remercier tous ceux qui m’ont apporté leur aide et leur soutien durant ces trois dernières années. Merci en premier lieu à mes directeurs de thèse, Joëlle Thollot et François Sillion, pour leur encadrement, écoute, conseils et même amitié. Il est difficile de rêver d’un meilleur tandem pour être accompagné lors de cette formation à la recherche. Je voudrais ensuite remercier l’équipe Artis pour sa cohésion, son atmosphère tant de travail que de franche camaraderie. Cela a été un immense plaisir que de travailler voire, il faut bien l’admettre, de vivre en son sein. Merci en particulier à mes « grandes soeurs et grands frères de thèse » : Adrien, Alex, Hed, David et Pascal. Vous m’aviez donné envie de me lancer dans cette aventure, et nos discus- sions n’ont ensuite eu de cesse que d’entretenir cette passion. Si je ne peux pas citer tous les membres de l’équipe, je tiens néanmoins à remercier explicitement mes collègues, et amis, de bureau et/ou de voyages conférences : Pierre, Thierry, Laurence, Cyril, Olivier, Charles, Nassim, Laurent et Kartic. Au-delà de l’équipe, j’ai eu la chance et le privilège de travailler avec de très nombreuses personnes que je souhaiterais également remercier. Merci tout d’abord à Ares Lagae, Peter Vangorp, Sylvain Lefebvre et George Drettakis pour m’avoir faire partager non seulement le stress d’une première deadline Siggraph, mais sur- tout les bières de Saarbrücken. I switch to English to thank Adam Finkelstein for the fantastic opportunities he opened up to me by welcoming me in Princeton. I would like to acknowledge all the members of the Princeton Graphics Group, with special thanks for Cynthia Lu and Martin Fuchs, which have made my stay at Princeton a pleasant and unforget- table experience. Last but not least, I thank Forrester Cole: it was a great pleasure and very enlightening to work with you. I would also like to acknowledge Aaron Hertzmann and Bernard Péroche for agreeing to evaluate my dissertation. In addition, I thank Marie-Paule Cani and Adam Finkelstein for being part of this committee and attending my defense. I am glad you came in Grenoble and gave me such insightful comments. Si mon existence ne s’est (heureusement) pas limitée à ma thèse, il faut en remercier mes amis : non seulement les anciens CPPistes et Ensimagiens pour nos dîners réguliers, mais aussi mes « petits du théâtre » – Adrien, Amélie, Valentine, Victor, Agnès, Chloé, Mathieu, Caroline, Pauline, Dimitri, Anne et Antoine – qui m’ont laissé les materner diriger. Enfin, je tiens à remercier mes parents, mes grands-parents et ma soeur pour leurs constants encouragements, leur intérêt pour mon travail, et leur compréhen- sion lors de mes, parfois bien longues, périodes de travail acharné. v PUBLICATIONS The work presented in this manuscript appeared previously in the following pub- lications: [BBT08] BÉNARD P., BOUSSEAU A., THOLLOT J.: Textures volumiques auto-zoomables pour une stylisation temporellement cohérente en temps réel. In AFIG ’08 (Actes des 21èmes journées de l’AFIG) (Nov. 2008). Best paper award. [BBT09] BÉNARD P., BOUSSEAU A., THOLLOT J.: Dynamic solid textures for real-time coherent stylization. In Proceedings of the 2009 sym- posium on Interactive 3D graphics and games - I3D ’09 (New York, New York, USA, 2009), ACM Press, p. 121. Best presentation award, 10.1145/1507149.1507169. [BCGF10] BÉNARD P., COLE F., GOLOVINSKIY A., FINKELSTEIN A.: Self- similar texture for coherent line stylization. In Proceedings of the 8th International Symposium on Non-Photorealistic Animation and Ren- dering - NPAR ’10 (New York, New York, USA, 2010), ACM Press, p. 91. Runner-up best paper award, 10.1145/1809939.1809950. [BLC∗10] BÉNARD P., LU C., COLE F., FINKELSTEIN A., THOLLOT J.: Con- tours actifs pour la stylisation cohérente de lignes animées. In AFIG ’10 (Actes des 23èmes journées de l’AFIG) (2010). Best paper award. [BLV∗10a] BÉNARD P., LAGAE A., VANGORP P., LEFEBVRE S., DRETTAKIS G., THOLLOT J.: A Dynamic Noise Primitive for Coherent Styl- ization. Computer Graphics Forum 29, 4 (Aug. 2010), 1497–1506. 10.1111/j.1467-8659.2010.01747.x. [BLV∗10b] BÉNARD P., LAGAE A., VANGORP P., LEFEBVRE S., DRETTAKIS G., THOLLOT J.: NPR Gabor noise for coherent stylization. In ACM SIGGRAPH 2010 Talks on - SIGGRAPH ’10 (New York, New York, USA, 2010), ACM Press, p.
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