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MeshCNN: a network with an edge

Published:12 July 2019Publication History
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Abstract

Polygonal meshes provide an efficient representation for 3D shapes. They explicitly captureboth shape surface and topology, and leverage non-uniformity to represent large flat regions as well as sharp, intricate features. This non-uniformity and irregularity, however, inhibits mesh analysis efforts using neural networks that combine convolution and pooling operations. In this paper, we utilize the unique properties of the mesh for a direct analysis of 3D shapes using MeshCNN, a convolutional neural network designed specifically for triangular meshes. Analogous to classic CNNs, MeshCNN combines specialized convolution and pooling layers that operate on the mesh edges, by leveraging their intrinsic geodesic connections. Convolutions are applied on edges and the four edges of their incident triangles, and pooling is applied via an edge collapse operation that retains surface topology, thereby, generating new mesh connectivity for the subsequent convolutions. MeshCNN learns which edges to collapse, thus forming a task-driven process where the network exposes and expands the important features while discarding the redundant ones. We demonstrate the effectiveness of MeshCNN on various learning tasks applied to 3D meshes.

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References

  1. Adobe. 2016. Adobe Fuse 3D Characters. https://www.mixamo.com.Google ScholarGoogle Scholar
  2. Dragomir Anguelov, Praveen Srinivasan, Daphne Koller, Sebastian Thrun, Jim Rodgers, and James Davis. 2005. SCAPE: Shape Completion and Animation of People. In ACM SIGGRAPH 2005 Papers (SIGGRAPH '05). ACM, New York, NY, USA, 408--416. Google ScholarGoogle ScholarDigital LibraryDigital Library
  3. James Atwood and Don Towsley. 2016. Diffusion-convolutional Neural Networks. In Proceedings of the 30th International Conference on Neural Information Processing Systems (NIPS'16). Curran Associates Inc., USA, 2001--2009. http://dl.acm.org/citation.cfm?id=3157096.3157320 Google ScholarGoogle ScholarDigital LibraryDigital Library
  4. Matan Atzmon, Haggai Maron, and Yaron Lipman. 2018. Point Convolutional Neural Networks by Extension Operators. ACM Trans. Graph. 37, 4 (July 2018), 71:1--71:12. Google ScholarGoogle ScholarDigital LibraryDigital Library
  5. Mark de Berg, Otfried Cheong, Marc van Kreveld, and Mark Overmars. 2008. Computational Geometry: Algorithms and Applications (3rd ed. ed.). Springer-Verlag TELOS, Santa Clara, CA, USA. Google ScholarGoogle ScholarDigital LibraryDigital Library
  6. Federica Bogo, Javier Romero, Matthew Loper, and Michael J Black. 2014. FAUST: Dataset and evaluation for 3D mesh registration. In Proceedings of the IEEE Conference on Computer Vision and Pattern Recognition. 3794--3801. Google ScholarGoogle ScholarDigital LibraryDigital Library
  7. Davide Boscaini, Jonathan Masci, Simone Melzi, Michael M Bronstein, Umberto Castellani, and Pierre Vandergheynst. 2015. Learning class-specific descriptors for deformable shapes using localized spectral convolutional networks. In Computer Graphics Forum, Vol. 34. Wiley Online Library, 13--23.Google ScholarGoogle Scholar
  8. Davide Boscaini, Jonathan Masci, Emanuele Rodolà, and Michael Bronstein. 2016. Learning shape correspondence with anisotropic convolutional neural networks. In Advances in Neural Information Processing Systems. 3189--3197. Google ScholarGoogle ScholarDigital LibraryDigital Library
  9. Mario Botsch, Leif Kobbelt, Mark Pauly, Pierre Alliez, and Bruno Lévy. 2010. Polygon mesh processing. AK Peters/CRC Press.Google ScholarGoogle Scholar
  10. Darko Bozidar and Tomaz Dobravec. 2015. Comparison of parallel sorting algorithms. CoRR abs/1511.03404 (2015).Google ScholarGoogle Scholar
  11. Andrew Brock, Theodore Lim, J.M. Ritchie, and Nick Weston. 2016. Generative and Discriminative Voxel Modeling with Convolutional Neural Networks. In NIPS 3D Deep Learning Workshop.Google ScholarGoogle Scholar
  12. Alexander M Bronstein, Michael M Bronstein, Leonidas J Guibas, and Maks Ovsjanikov. 2011. Shape google: Geometric words and expressions for invariant shape retrieval. ACM Transactions on Graphics (TOG) 30, 1 (2011), 1. Google ScholarGoogle ScholarDigital LibraryDigital Library
  13. Michael M. Bronstein, Joan Bruna, Yann LeCun, Arthur Szlam, and Pierre Vandergheynst. 2017. Geometric Deep Learning: Going beyond Euclidean data. IEEE Signal Process. Mag. 34, 4 (2017), 18--42.Google ScholarGoogle ScholarCross RefCross Ref
  14. Joan Bruna, Wojciech Zaremba, Arthur Szlam, and Yann LeCun. 2014. Spectral Networks and Locally Connected Networks on Graphs. In International Conference on Learning Representations (ICLR).Google ScholarGoogle Scholar
  15. C. Cangea, P. Velickovic, N. Jovanovic, T. Kipf, and P. Lio. 2018. Towards Sparse Hierarchical Graph Classifiers. In NeurIPS Workshop on Relational Representation Learning.Google ScholarGoogle Scholar
  16. Liang-Chieh Chen, George Papandreou, Iasonas Kokkinos, Kevin Murphy, and Alan L Yuille. 2018. Deeplab: Semantic image segmentation with deep convolutional nets, atrous convolution, and fully connected crfs. IEEE transactions on pattern analysis and machine intelligence 40, 4 (2018), 834--848.Google ScholarGoogle Scholar
  17. Michaël Defferrard, Xavier Bresson, and Pierre Vandergheynst. 2016. Convolutional neural networks on graphs with fast localized spectral filtering. In Advances in Neural Information Processing Systems. 3844--3852. Google ScholarGoogle ScholarDigital LibraryDigital Library
  18. Danielle Ezuz, Justin Solomon, Vladimir G. Kim, and Mirela Ben-Chen. 2017. GWCNN: A Metric Alignment Layer for Deep Shape Analysis. Computer Graphics Forum (2017). Google ScholarGoogle ScholarDigital LibraryDigital Library
  19. Xifeng Gao, Daniele Panozzo, Wenping Wang, Zhigang Deng, and Guoning Chen. 2017. Robust structure simplification for hex re-meshing. ACM Transactions on Graphics 36, 6 (2017). Google ScholarGoogle ScholarDigital LibraryDigital Library
  20. Michael Garland and Paul S Heckbert. 1997. Surface simplification using quadric error metrics. In Proceedings of the 24th annual conference on Computer graphics and interactive techniques. ACM Press/Addison-Wesley Publishing Co., 209--216. Google ScholarGoogle ScholarDigital LibraryDigital Library
  21. Daniela Giorgi, Silvia Biasotti, and Laura Paraboschi. 2007. Shape retrieval contest 2007: Watertight models track. SHREC competition 8, 7 (2007).Google ScholarGoogle Scholar
  22. Francisco Gomez-Donoso, Alberto Garcia-Garcia, J Garcia-Rodriguez, Sergio Orts-Escolano, and Miguel Cazorla. 2017. Lonchanet: A sliced-based cnn architecture for real-time 3d object recognition. In 2017 International Joint Conference on Neural Networks (IJCNN). IEEE, 412--418.Google ScholarGoogle ScholarCross RefCross Ref
  23. Benjamin Graham, Martin Engelcke, and Laurens van der Maaten. 2017. 3D Semantic Segmentation with Submanifold Sparse Convolutional Networks. CoRR abs/1711.10275 (2017).Google ScholarGoogle Scholar
  24. Paul Guerrero, Yanir Kleiman, Maks Ovsjanikov, and Niloy J. Mitra. 2018. PCPNet: Learning Local Shape Properties from Raw Point Clouds. Computer Graphics ForumGoogle ScholarGoogle Scholar
  25. 37, 2 (2018), 75--85.Google ScholarGoogle Scholar
  26. Niv Haim, Nimrod Segol, Heli Ben-Hamu, Haggai Maron, and Yaron Lipman. 2018. Surface Networks via General Covers. CoRR abs/1812.10705 (2018).Google ScholarGoogle Scholar
  27. Rana Hanocka, Noa Fish, Zhenhua Wang, Raja Giryes, Shachar Fleishman, and Daniel Cohen-Or. 2018. ALIGNet: Partial-Shape Agnostic Alignment via Unsupervised Learning. ACM Trans. Graph. 38, 1, Article 1 (Dec. 2018), 14 pages. Google ScholarGoogle ScholarDigital LibraryDigital Library
  28. Mikael Henaff, Joan Bruna, and Yann LeCun. 2015. Deep Convolutional Networks on Graph-Structured Data. CoRR abs/1506.05163 (2015).Google ScholarGoogle Scholar
  29. Hugues Hoppe. 1997. View-dependent refinement of progressive meshes. In Proceedings of the 24th annual conference on Computer graphics and interactive techniques. ACM Press/Addison-Wesley Publishing Co., 189--198. Google ScholarGoogle ScholarDigital LibraryDigital Library
  30. Hugues Hoppe. 1999. New quadric metric for simplifying meshes with appearance attributes. In Visualization'99. Proceedings. IEEE, 59--510. Google ScholarGoogle ScholarDigital LibraryDigital Library
  31. Hugues Hoppe, Tony DeRose, Tom Duchamp, John McDonald, and Werner Stuetzle. 1993. Mesh optimization., 19--26 pages. Google ScholarGoogle ScholarDigital LibraryDigital Library
  32. Yangqing Jia. 2014. Learning Semantic Image Representations at a Large Scale. (2014).Google ScholarGoogle Scholar
  33. Chiyu Max Jiang, Jingwei Huang, Karthik Kashinath, Prabhat, Philip Marcus, and Matthias Niessner. 2019. Spherical CNNs on Unstructured Grids. In International Conference on Learning Representations. https://openreview.net/forum?id=Bkl-43C9FQGoogle ScholarGoogle Scholar
  34. Evangelos Kalogerakis, Melinos Averkiou, Subhransu Maji, and Siddhartha Chaudhuri. 2017. 3D shape segmentation with projective convolutional networks. In Proc. CVPR, Vol. 1. 8.Google ScholarGoogle Scholar
  35. Evangelos Kalogerakis, Aaron Hertzmann, and Karan Singh. 2010. Learning 3D mesh segmentation and labeling. ACM Transactions on Graphics (TOG) 29, 4 (2010), 102. Google ScholarGoogle ScholarDigital LibraryDigital Library
  36. I. Kokkinos, M. M. Bronstein, R. Litman, and A. M. Bronstein. 2012. Intrinsic shape context descriptors for deformable shapes. In IEEE Conference on Computer Vision and Pattern Recognition (CVPR). 159--166. Google ScholarGoogle ScholarDigital LibraryDigital Library
  37. Ilya Kostrikov, Zhongshi Jiang, Daniele Panozzo, Denis Zorin, and Burna Joan. 2018. Surface Networks. In IEEE Conference on Computer Vision and Pattern Recognition (CVPR).Google ScholarGoogle Scholar
  38. Alex Krizhevsky, Ilya Sutskever, and Geoffrey E Hinton. 2012. Imagenet classification with deep convolutional neural networks. In Advances in neural information processing systems. 1097--1105. Google ScholarGoogle ScholarDigital LibraryDigital Library
  39. Longin Jan Latecki and Rolf Lakamper. 2000. Shape similarity measure based on correspondence of visual parts. IEEE Transactions on Pattern Analysis and Machine Google ScholarGoogle ScholarDigital LibraryDigital Library
  40. Intelligence 22, 10 (2000), 1185--1190. Google ScholarGoogle ScholarDigital LibraryDigital Library
  41. Yann LeCun. 2012. Learning invariant feature hierarchies. In European conference on computer vision. Springer, 496--505. Google ScholarGoogle ScholarDigital LibraryDigital Library
  42. Yangyan Li, Rui Bu, Mingchao Sun, and Baoquan Chen. 2018. PointCNN. CoRR abs/1801.07791 (2018).Google ScholarGoogle Scholar
  43. Yangyan Li, Soren Pirk, Hao Su, Charles R Qi, and Leonidas J Guibas. 2016. FPNN: Field probing neural networks for 3D data. In Advances in Neural Information Processing Systems (NIPS). 307--315. Google ScholarGoogle ScholarDigital LibraryDigital Library
  44. Z Lian, A Godil, B Bustos, M Daoudi, J Hermans, S Kawamura, Y Kurita, G Lavoua, and P Dp Suetens. 2011. Shape retrieval on non-rigid 3D watertight meshes. In Eurographics Workshop on 3D Object Retrieval (3DOR). Google ScholarGoogle ScholarDigital LibraryDigital Library
  45. Or Litany, Alexander M. Bronstein, Michael M. Bronstein, and Ameesh Makadia. 2018. Deformable Shape Completion With Graph Convolutional Autoencoders. In CVPR.Google ScholarGoogle Scholar
  46. Haggai Maron, Meirav Galun, Noam Aigerman, Miri Trope, Nadav Dym, Ersin Yumer, Vladimir G Kim, and Yaron Lipman. 2017. Convolutional neural networks on surfaces via seamless toric covers. ACM Trans. Graph 36, 4 (2017), 71. Google ScholarGoogle ScholarDigital LibraryDigital Library
  47. Jonathan Masci, Davide Boscaini, Michael Bronstein, and Pierre Vandergheynst. 2015. Geodesic convolutional neural networks on riemannian manifolds. In Proceedings of the IEEE international conference on computer vision workshops. 37--45. Google ScholarGoogle ScholarDigital LibraryDigital Library
  48. Federico Monti, Davide Boscaini, Jonathan Masci, Emanuele Rodola, Jan Svoboda, and Michael M Bronstein. 2017. Geometric deep learning on graphs and manifolds using mixture model CNNs. In Proc. CVPR, Vol. 1. 3.Google ScholarGoogle ScholarCross RefCross Ref
  49. Federico Monti, Oleksandr Shchur, Aleksandar Bojchevski, Or Litany, Stephan Gunnemann, and Michael M. Bronstein. 2018. Dual-Primal Graph Convolutional Networks. CoRR abs/1806.00770 (2018).Google ScholarGoogle Scholar
  50. Mathias Niepert, Mohamed Ahmed, and Konstantin Kutzkov. 2016. Learning Convolutional Neural Networks for Graphs. In International Conference on Machine Learning (ICML). Google ScholarGoogle ScholarDigital LibraryDigital Library
  51. Adam Paszke, Sam Gross, Soumith Chintala, Gregory Chanan, Edward Yang, Zachary DeVito, Zeming Lin, Alban Desmaison, Luca Antiga, and Adam Lerer. 2017. Automatic differentiation in PyTorch. In NIPS-W.Google ScholarGoogle Scholar
  52. Adrien Poulenard and Maks Ovsjanikov. 2018. Multi-directional Geodesic Neural Networks via Equivariant Convolution. In SIGGRAPH Asia 2018 Technical Papers (SIGGRAPH Asia '18). ACM, New York, NY, USA, Article 236, 14 pages. Google ScholarGoogle ScholarDigital LibraryDigital Library
  53. Charles R Qi, Hao Su, Kaichun Mo, and Leonidas J Guibas. 2017a. Pointnet: Deep learning on point sets for 3d classification and segmentation. Proc. Computer Vision and Pattern Recognition (CVPR), IEEE 1, 2 (2017), 4.Google ScholarGoogle Scholar
  54. Charles R. Qi, Hao Su, Matthias Niessner, Angela Dai, Mengyuan Yan, and Leonidas J. Guibas. 2016. Volumetric and multi-view CNNs for object classification on 3d data. In Computer Vision and Pattern Recognition (CVPR). 5648--5656.Google ScholarGoogle Scholar
  55. Charles R. Qi, Li Yi, Hao Su, and Leonidas J Guibas. 2017b. PointNet++: Deep Hierarchical Feature Learning on Point Sets in a Metric Space. In Advances in Neural Information Processing Systems (NIPS). 5105--5114. Google ScholarGoogle ScholarDigital LibraryDigital Library
  56. Anurag Ranjan, Timo Bolkart, Soubhik Sanyal, and Michael J. Black. 2018. Generating 3D faces using Convolutional Mesh Autoencoders. In European Conference on Computer Vision (ECCV). Springer International Publishing, 725--741.Google ScholarGoogle Scholar
  57. Gernot Riegler, Ali Osman Ulusoy, and Andreas Geiger. 2017. OctNet: Learning deep 3D representations at high resolutions. In Computer Vision and Pattern Recognition (CVPR).Google ScholarGoogle Scholar
  58. Olaf Ronneberger, Philipp Fischer, and Thomas Brox. 2015. U-net: Convolutional networks for biomedical image segmentation. In International Conference on Medical image computing and computer-assisted intervention. Springer, 234--241.Google ScholarGoogle ScholarCross RefCross Ref
  59. Szymon Rusinkiewicz and Marc Levoy. 2000. QSplat: A Multiresolution Point Rendering System for Large Meshes. In Proceedings of the 27th Annual Conference on Computer Graphics and Interactive Techniques (SIGGRAPH '00). ACM Press/Addison-Wesley Publishing Co., New York, NY, USA, 343--352. Google ScholarGoogle ScholarDigital LibraryDigital Library
  60. Kripasindhu Sarkar, Basavaraj Hampiholi, Kiran Varanasi, and Didier Stricker. 2018. Learning 3D Shapes as Multi-Layered Height-maps using 2D Convolutional Networks. In Proceedings of the European Conference on Computer Vision (ECCV). 71--86.Google ScholarGoogle ScholarCross RefCross Ref
  61. Pierre Sermanet, David Eigen, Xiang Zhang, Michaël Mathieu, Rob Fergus, and Yann LeCun. 2013. Overfeat: Integrated recognition, localization and detection using convolutional networks. arXiv preprint arXiv:1312.6229 (2013).Google ScholarGoogle Scholar
  62. Karen Simonyan and Andrew Zisserman. 2014. Very deep convolutional networks for large-scale image recognition. arXiv preprint arXiv:1409.1556 (2014).Google ScholarGoogle Scholar
  63. Ayan Sinha, Jing Bai, and Karthik Ramani. 2016. Deep learning 3D shape surfaces using geometry images. In European Conference on Computer Vision. Springer, 223--240.Google ScholarGoogle ScholarCross RefCross Ref
  64. Hang Su, Subhransu Maji, Evangelos Kalogerakis, and Erik Learned-Millers. 2015. Multi-view Convolutional Neural Networks for 3D Shape Recognition. In International Conference on Computer Vision (ICCV). Google ScholarGoogle ScholarDigital LibraryDigital Library
  65. F. P. Such, S. Sah, M. A. Dominguez, S. Pillai, C. Zhang, A. Michael, N. D. Cahill, and R. Ptucha. 2017. Robust Spatial Filtering With Graph Convolutional Neural Networks. IEEE Journal of Selected Topics in Signal Processing 11, 6 (Sept 2017), 884--896.Google ScholarGoogle ScholarCross RefCross Ref
  66. Marco Tarini, Nico Pietroni, Paolo Cignoni, Daniele Panozzo, and Enrico Puppo. 2010. Practical quad mesh simplification. In Computer Graphics Forum, Vol. 29. Wiley Online Library, 407--418.Google ScholarGoogle Scholar
  67. Maxim Tatarchenko, Jaesik Park, Vladlen Koltun, and Qian-Yi Zhou. 2018. Tangent Convolutions for Dense Prediction in 3D. In Proceedings of the IEEE Conference on Computer Vision and Pattern Recognition. 3887--3896.Google ScholarGoogle ScholarCross RefCross Ref
  68. Lyne P. Tchapmi, Christopher B. Choy, Iro Armeni, JunYoung Gwak, and Silvio Savarese. 2017. SEGCloud: Semantic Segmentation of 3D Point Clouds. In 3DV.Google ScholarGoogle Scholar
  69. Petar Velickovic, Guillem Cucurull, Arantxa Casanova, Adriana Romero, Pietro Lio, and Yoshua Bengio. 2018. Graph Attention Networks. In International Conference on Learning Representations.Google ScholarGoogle Scholar
  70. Nitika Verma, E. Boyer, and Jakob Verbeek. 2018. FeaStNet: Feature-Steered Graph Convolutions for 3D Shape Analysis. In CVPR.Google ScholarGoogle Scholar
  71. Daniel Vlasic, Ilya Baran, Wojciech Matusik, and Jovan Popović. 2008. Articulated mesh animation from multi-view silhouettes. In ACM Transactions on Graphics (TOG), Vol. 27. ACM, 97. Google ScholarGoogle ScholarDigital LibraryDigital Library
  72. Peng-Shuai Wang, Yang Liu, Yu-Xiao Guo, Chun-Yu Sun, and Xin Tong. 2017. OCNN: Octree-based Convolutional Neural Networks for 3D Shape Analysis. ACM Trans. Graph. 36, 4, Article 72 (July 2017), 11 pages. Google ScholarGoogle ScholarDigital LibraryDigital Library
  73. Yunhai Wang, Shmulik Asafi, Oliver van Kaick, Hao Zhang, Daniel Cohen-Or, and Baoquan Chen. 2012. Active co-analysis of a set of shapes. ACM Transactions on Graphics (TOG) 31, 6 (2012), 165. Google ScholarGoogle ScholarDigital LibraryDigital Library
  74. Yue Wang, Yongbin Sun, Ziwei Liu, Sanjay E Sarma, Michael M Bronstein, and Justin M Solomon. 2018a. Dynamic graph CNN for learning on point clouds. arXiv preprint arXiv:1801.07829 (2018).Google ScholarGoogle Scholar
  75. Yue Wang, Yongbin Sun, Ziwei Liu, Sanjay E Sarma, Michael M Bronstein, and Justin M Solomon. 2018b. Dynamic Graph CNN for Learning on Point Clouds. arXiv preprint arXiv:1801.07829 (2018).Google ScholarGoogle Scholar
  76. Francis Williams, Teseo Schneider, Claudio Silva, Denis Zorin, Joan Bruna, and Daniele Panozzo. 2018. Deep Geometric Prior for Surface Reconstruction. arXiv preprint arXiv:1811.10943 (2018).Google ScholarGoogle Scholar
  77. Zhirong Wu, Shuran Song, Aditya Khosla, Fisher Yu, Linguang Zhang, Xiaoou Tang, and Jianxiong Xiao. 2015. 3D shapenets: A deep representation for volumetric shapes. In Computer Vision and Pattern Recognition (CVPR). 1912--1920.Google ScholarGoogle Scholar
  78. Haotian Xu, Ming Dong, and Zichun Zhong. 2017. Directionally Convolutional Networks for 3D Shape Segmentation. In Proceedings of the IEEE International Conference on Computer Vision. 2698--2707.Google ScholarGoogle ScholarCross RefCross Ref
  79. Li Yi, Hao Su, Xingwen Guo, and Leonidas Guibas. 2017. SyncSpecCNN: Synchronized Spectral CNN for 3D Shape Segmentation. In Computer Vision and Pattern Recognition (CVPR).Google ScholarGoogle Scholar
  80. Zhitao Ying, Jiaxuan You, Christopher Morris, Xiang Ren, Will Hamilton, and Jure Leskovec. 2018. Hierarchical Graph Representation Learning with Differentiable Pooling. In Advances in Neural Information Processing Systems. 4805--4815. Google ScholarGoogle ScholarDigital LibraryDigital Library
  81. Tinghui Zhou, Richard Tucker, John Flynn, Graham Fyffe, and Noah Snavely. 2018. Stereo Magnification: Learning View Synthesis Using Multiplane Images. ACM Trans. Graph. 37, 4 (July 2018), 65:1--65:12. Google ScholarGoogle ScholarDigital LibraryDigital Library

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        cover image ACM Transactions on Graphics
        ACM Transactions on Graphics  Volume 38, Issue 4
        August 2019
        1480 pages
        ISSN:0730-0301
        EISSN:1557-7368
        DOI:10.1145/3306346
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        • Published: 12 July 2019
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