We are trying to use the fairly recent VTK Lagrange cells (specifically, quadrilaterals and hexahedrals). However, some things are not clear to me and I couldn’t find any documentation on it:
- Is it possible to specify only point data for such cells or also cell data? If cell data is allowed - how many data values per cell can be added? I assume that they should match the number of points in the cell, but how can one then distinguish between point data and cell data?
- How to visualize unstructured, discontinuous data on Lagrange quadrilaterals? Specifically, if I use the same points on an edge that is shared by two quadrilaterals, how to specify values at the boundary from the two adjacent cells? Using “classic” VTK cells, I typically made sure that neighboring cells that share vertices/edges/faces also reuse the same points, since I assume that this is required for VTK to understand the connectivity between cells when calculating gradients etc. However, in case of discontinuous Galerkin solutions, I would lose the ability to specify values at the boundary from each cells, effectively losing some information in the process. Thus, what’s the proper way to go about this?
I apologize if this has been answered before, and if there’s already some form of documentation on these questions, I’d greatly appreciate a reference to it!