[vtkusers] filter to pass one (cell or point) array

[Rodrigo Valiña Gutiérrez]

Hi,

I have several sources, some ones read with vtkUnstructuredGridReader,
and others read with vtkXMLUnstructuredGridReader.

I wanted to use the same source object to feed other filters and
finally plot some data: say the file has as point data "pressure" and
"temperature" and some other arrays as cell data.

I want to plot several times, some ones with the "pressure" array,
some others with another array, at the same time.

Now I am creating a vtkUnstructuredGridReader object for each field I
want to plot, even of the same file, and I am setting the active
scalars or vectors for that object corresponding to what I want to
plot.

If I create only one vtkUnstructuredGridReader, is there any filter
that only passes the field I want (say "temperature")?

Then I would have several (light) filters like that, and only one
vtkUnstructuredGridReader that would hold most data (and no need to
read the file several times)

I can not create one vtkUnstructuredGridReader and change active
scalars each time I want to plot, since I must have several plots open
(in tabs).

I want the filter to have GetOutput() and GetOutputPort()