We propose an end-to-end pipeline to robustly generate high-quality quadrilateral meshes for complex CAD models. An initial quad-dominant mesh is generated with frontal point insertion guided by a locally integrable cross field and a scalar size map adapted to the small CAD features. After triangle combination and midpoint-subdivision into an all-quadrilateral mesh, the topology of the mesh is modified to reduce the number of irregular vertices. The idea is to preserve the irregular vertices matching cross-field singularities and to eliminate the others. The topological modifications are either local and based on disk quadrangulations, or more global with the remeshing of patches of quads according to predefined patterns. Validity of the quad mesh is guaranteed by monitoring element quality during all operations and reverting the changes when necessary. Advantages of our approach include robustness, strict respect of the CAD features and support for user-prescribed size constraints. The quad mesher, which is available in Gmsh, is validated and illustrated on two datasets of CAD models.

中文翻译：

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Gmsh中的准结构四边形网格划分-复杂CAD模型的强大流水线

我们提出了一条端到端的管道，以针对复杂的CAD模型稳健地生成高质量的四边形网格。生成最初的四支网格，并通过局部可积分的交叉场和适合于小型CAD特征的标量尺寸图引导前额点插入。在将三角形组合和中点细分成全四边形网格之后，对网格的拓扑进行修改以减少不规则顶点的数量。想法是保留与跨场奇点匹配的不规则顶点，并消除其他顶点。拓扑修改既可以是局部的，也可以基于磁盘四边形，也可以是更全局的，可以根据预定义的模式对四边形的补丁进行重新划分。通过在所有操作期间监视元素质量并在必要时还原更改，可以确保四边形网格的有效性。我们方法的优点包括健壮性，对CAD功能的严格尊重以及对用户指定的大小限制的支持。已在Gmsh中使用的Quad Mesher经过验证，并在两个CAD模型数据集中进行了说明。