[vtkusers] Trouble Applying Threshold filter to UnstructuredGrid

[Mike Jackson]

I have a vtkUnstructuredGrid with 5 sets of Scalars attached to the  
point data. I would like to run a vtkThreshold filter on the grid  
selecting only points from the grid that have a scalar value between  
1.5 and 2.5. I only want to use the 3rd scalar array as the  
determining factor.

So lets say that I named my scalars "Scalars 1", "Scalars 2"...

Here is what I have so far, which is not working.

vtkSmartPointer<vtkThreshold> thr = vtkSmartPointer<vtkThreshold>::New 
();
vtkFieldData* fd = grid->GetFieldData();
int index = -1;
fd->GetArray("Scalars 3", index);
thr->SetInput(grid);
thr->ThresholdBetween( 1.5, 2.5 );
thr->AllScalarsOff();
thr->SetInputArrayToProcess(index, info);
thr->Update(); // Force the filter to run
vtkUnstructuredGrid* output = thr->GetOutput(0);
output->Register(NULL);

Note that I am using "info" variable which was retrieved from the  
RequestData(.. ) arguments in the usual fashion, which I don't think  
is correct.

Also, the index of the Scalars array comes back as "-1" which means  
that my "Scalars 3" array could not be found. I know it is there. I  
can print the vtkUnstructuredGrid and "see" the named array.

So I know this should be straight forward but I am just coming up empty.

Any help or hints would be appreciated.
--
Mike Jackson
imikejackson & gmail * com