Scatter in worklets
Add the functionality to perform a scatter operation from input to output in a worklet invocation. This allows you to, for example, specify a variable amount of outputs generated for each input.
See merge request !221
Recent changes to algorithm implementations caused CellDerivative to be
called in a way such that it gave conversion warnings on some compilers.
Fix that.
These cell types are inherited from VTK, but they are basically the same
as quad and hexahedron, respectively. The only useful difference is that
pixel and voxel are supposed to be axis aligned, but you cannot
determine that by the cell shape alone (at least not just from the cell
set).
A big issue with these is that their indexing is different that of quad
and hex. The development team had a long discussion about the benefits
of the alternate indexing, but after consulting with Berk Geveci and
Will Schroder from the VTK team, that indexing is not really taken
advantage of at the cell level. Thus, it is really just a nuisance in
VTK-m.
The original way was overconstrained with respect to the number of
parametric coordinates.
Also implemented WorldCoordinatesToParametricCoordinates for polygons.
The general polygon version is not implemented yet because I need to
change the way it is interpolated.
To get wedge to work correctly, I had to change the interpolation
slightly there. Previously the interpolation had a singularity at
the tip.
The functions for doing interpolations and derivatives were called
CellInterpolate and CellDerivative, but the file names were
Interpolate.h and Derivative. Now the files are CellInterpolate.h and
CellDerivative.h so they are more consistent and a bit easier to find.
The interpolate and derivative functions has the shape tag at end of the
function arguments (just before the "worklet" parameter, which is just
the error handling mechanism). However, the parametric coordinate
functions had the shape tag at the beginning. Moved the shape tag to the
end to be more consistent within these functions and also in other uses
throughtout VTK-m.
