Composite Data Sets for the VTKHDF format

[danlipsa (Dan Lipsa (Kitware))]

@jfausty

Conceptually, given the partitioning present already in the PolyData and UnstructuredGrid formats, the blocks can already be treated as Partitioned Data Sets. This is what is reflected in this: https://gitlab.kitware.com/vtk/vtk/-/merge_requests/10355 relatively new development. The Option MergeParts turns the output into a Partitioned Data Set when deactivated. As such, those two levels are already baked into the format, are well separated into two mechanisms and conceptually correspond to the division between vtkPartitionedDataSetCollection and vtkPartitionedDataSet.

I see. That’s great! What do you do for ImageData? Is that also considered a partitioned dataset?

@jfausty

Yep, this is indeed what is represented in the diagram above by the special Assembly group. The names associated to each node of the tree are the names of the groups and blocks. This might be unclear in the representation and any suggestions for making it clearer are welcome.

Sounds good. What happens when you save a PD collection that does not have a data assembly. How do you come up with the names for the PDs? Based on index?

@jfausty

I am not sure I follow. There is a one to one correspondence between multi-block and PD collection, is there not? What information is being lost in the conversion? In the multi-block structure each block still has a name, right?

I never used names for multiblock. What is the API to set/get names of nodes in the tree?