Hi all,
let me briefly introduce the context for my question.
We are using VTK as the geometry / post-processing engine for our application: our data is represented by a vtkUnstructuredGrid made of 2D/3D cells (both linear and non-linear) and we use filters to run all kinds of operations such as thresholding, clipping with other geometry, extracting isocontours, generating section cuts, etc… On the other hand, we don’t use VTK as a visualization engine so we always convert the output datasets to an internal format for rendering within our own graphics engine.
All has been good so far, but there is a new requirement to support data values on the corners of a cell. These should behave similarly to point data (e.g. interpolated across the cell) but if multiple cells are sharing the same vertex it must allow each cell to have a different value for that point. (See image below)
Do you have any suggestions on how to achieve this with VTK ? Again, we don’t need this implemented on the visualization side but just in terms of geometry post-processing.
I guess that we could duplicate all shared vertices and have a different set of points for each cell, so that regular point data would behave as corner data. The obvious downside of this approach is that we lose topological connectivity between cells which will break a bunch of other things (e.g. vtkGeometryFilter for 3D cells will consider each cell face as external, vtkFeatureEdges will consider each edge as boundary, etc…), correct ?
In my research I’ve also found some discussions about vtkDGCell types which seem to be tackling a similar (although probably even more complex) problem. References: link1, link2, link3.
I’m afraid I don’t have the mathematical background to properly understand what this Discontinuous Galerkin method is all about, but it seems like a superset of what we’re trying to achieve. Also, I’ve seen mentions of this Finite Element Field Distributor (FEFD) filter in ParaView but I can’t find any documentation about it.
My main concern with is whether all existing filters that we use are going to support this vtkDGCell or not, and how expensive it would be.
Any help on this topic would be much appreciated,.
Thanks in advance,
-PaoloG