Sheet module description

In this module, we provide the usual operations that can be safely performed on quad or hex mesh. By safely, we means that the mesh remains a full quad, respectively hex mesh after performing a sheet operation.

We provide the 3 basic operations, which are: - Sheet selection. Giving 2 nodes, or an edge, it returns the set of cells that belongs to the corresponding sheet. - Sheet collapse. Giving 2 nodes, or an edge, it removes the corresponding sheet from the mesh. - Sheet pillow. Giving a path of edges or a convex set of cells, it inserts a sheet inside the mesh.

Requirements

Sheet collapse and pillow are operations that modify the mesh. They are quite easy to implement if you only consider the mesh structure but taking geometric classification makes it more tricky to handle.

Geometric classification requires to handle a few special cases where faces (in 3D) and edges (in 2D) are required along the mesh boundary. It means that we restrict our implementation to mesh where: - in 2D, boundary edges must be defined in the mesh and connection E2N at least. We do not use the N2E connectivity because it enforces all the mesh nodes to store an indirection to a potential list of adjacent edges. - in 23D, boundary faces and edges must be defined in the mesh and connections F2N and E2N at least