The version of `Filter::Execute` that takes a policy as an argument is now
deprecated. Filters are now able to specify their own fields and types,
which is often why you want to customize the policy for an execution. The
other reason is that you are compiling VTK-m into some other source that
uses a particular types of storage. However, there is now a mechanism in
the CMake configuration to allow you to provide a header that customizes
the "default" types used in filters. This is a much more convenient way to
compile filters for specific types.
One thing that filters were not able to do was to customize what cell sets
they allowed using. This allows filters to self-select what types of cell
sets they support (beyond simply just structured or unstructured). To
support this, the lists `SupportedCellSets`, `SupportedStructuredCellSets`,
and `SupportedUnstructuredCellSets` have been added to `Filter`. When you
apply a policy to a cell set, you now have to also provide the filter.
VTK-m now provides the following filters with the default policy
as part of the vtkm_filter library:
- CellAverage
- CleanGrid
- ClipWithField
- ClipWithImplicitFunction
- Contour
- ExternalFaces
- ExtractStructured
- PointAverage
- Threshold
- VectorMagnitude
By building these as a library we hope to provide faster compile
times for consumers of VTK-m when using common configurations.
Previously, all the ApplyPolicy functions had the same name and used
template resolution to figure out which one to use. This was pretty
clear at first when there was just one for fields and one for cell sets.
But then it grew to several different types, particularly for fields. It
was hard to look at the code and figure out which form of ApplyPolicy
was being used, and compilers were starting to get confused.
Resolve the problem by giving all the methods unique names to make it
clear which one you expect to be called.
By removing the ability to have multiple CellSets in a DataSet
we can simplify the following things:
- Cell Fields now don't require a CellSet name when being constructed
- Filters don't need to manage what the active cellset is
