GAMES Webinar 2018-57期（Siggraph 2018论文）| 武奎（犹他大学），刘衡（亚琛工业大学)
【GAMES Webinar 2018-57期（Siggraph 2018论文）】
报告时间：2018年7月26日（星期四）晚8:00 – 8:45（北京时间）
We introduce the first fully automatic pipeline to convert arbitrary 3D shapes into knit models. Our pipeline is based on a global parametrization remeshing pipeline to produce an isotropic quad-dominant mesh aligned with a 2-RoSy field. The knitting directions over the surface are determined using a set of custom topological operations and a two-step global optimization that minimizes the number of irregularities. The resulting mesh is converted into a valid stitch mesh that represents the knit model. The yarn curves are generated from the stitch mesh and the final yarn geometry is computed using a yarn-level relaxation process. Thus, we produce topologically valid models that can be used with a yarn-level simulation. We validate our algorithm by automatically generating knit models from complex 3D shapes and processing over a hundred models with various shapes without any user input or parameter tuning. We also demonstrate applications of our approach for custom knit model generation using fabrication via 3D printing.
Kui Wu is a Ph.D. candidate in the School of Computing, advised by Dr. Cem Yuksel. He is from Qingdao, China. His research interests are in computer graphics and related fields, including GPU algorithms, knitted structures modeling, and real-time rendering and simulation techniques.
报告时间：2018年7月26日（星期四）晚8:45 – 9:30（北京时间）
报告题目：Singularity-Constrained Octahedral Field for Hexahedral Meshing
Despite high practical demand, algorithmic hexahedral meshing with guarantees on robustness and quality remains unsolved. A promising direction follows the idea of integer-grid maps, which pull back the Cartesian hexahedral grid formed by integer isoplanes from a parametric domain to a surface-conforming hexahedral mesh of the input object. Since directly optimizing for a high-quality integer-grid map is mathematically challenging, the construction is usually split into two steps: (1) generation of a surface-aligned octahedral field and (2) generation of an integer-grid map that best aligns to the octahedral field. The main robustness issue stems from the fact that smooth octahedral fields frequently exhibit singularity graphs that are not appropriate for hexahedral meshing and induce heavily degenerate integer-grid maps. The first contribution of this work is an enumeration of all local configurations that exist in hex meshes with bounded edge valence, and a generalization of the Hopf-Poincaré formula to octahedral fields, leading to necessary local and global conditions for the hex-meshability of an octahedral field in terms of its singularity graph. The second contribution is a novel algorithm to generate octahedral fields with prescribed hex-meshable singularity graphs, which requires the solution of a large non-linear mixed-integer algebraic system. This algorithm is an important step toward robust automatic hexahedral meshing since it enables the generation of a hex-meshable octahedral field.
Heng Liu is currently a Ph.D. student in computer science at RWTH Aachen University, advised by Prof. David Bommes. His research interests are mainly on geometry processing and computer graphics, in particular mesh generation and optimization.
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