Data type casting between integer and floating point types

[moritz-h]

I think it should be possible to cast between integer and floating point types in tpf_data, but I'm not 100% sure if this simply can be changes without side effects.

The problem is, that the ParaView plugin cannot read grids with grid coordinates stored as integers.

The point type is i.e. hardcoded here as floating point type:

tpf/src/paraview/basic/modules/plic/tpf_plic.cpp

Line 66 in def9ba3

const auto vof = tpf::vtk::get_grid<float_t, float_t, 3, 1>(in_grid, tpf::data::topology_t::CELL_DATA, this->GetInputArrayToProcess(0, in_grid));

The grid coordinates are extracted here:

tpf/include/tpf/vtk/tpf_grid.inl

Line 60 in def9ba3

node_coordinates.push_back(get_data<point_t, vtkFloatArray>(grid->GetXCoordinates(), std::string("X coordinates")));

So basically the array is read and should be casted to point_t. (side note: i think vtkFloatArray should be changed to vtk_array<point_t>::type)

And finally the dynamic casting happens here:

tpf/include/tpf/vtk/tpf_data.inl

Lines 127 to 142 in def9ba3

	if (std::is_floating_point<value_t>::value)
	{
	// Try double and float
	switch (data->GetDataType())
	{
	case VTK_FLOAT:
	warn_mismatch<value_t, float>(array_name);
	return get_data<value_t, typename vtk_array<float>::type, false>(data, array_name);
	case VTK_DOUBLE:
	warn_mismatch<value_t, double>(array_name);
	return get_data<value_t, typename vtk_array<double>::type, false>(data, array_name);
	}
	}
	else if (std::is_integral<value_t>::value && std::is_signed<value_t>::value)

The problem is when point_t is floating point, the array is expected to contain float or double values. But I think it should also cast any integer array type to point_t. In general casting int to float should not be worse than casting double to float. Warnings about the precision lost are thrown anyway.
But this is only the perspective from the grid coordinates array, this function probably is also used for data arrays in general and I don't know if casting is then wanted in all cases.