[vtkusers] vtkThreshold - how it works?

[rakesh patil]

Hello,

What will happen in the following case?

vtkSmartPointer<vtkGeometryFilter> gf =
vtkSmartPointer<vtkGeometryFilter>::New();
gf->SetInput(unGrid);

vtkSmartPointer<vtkThreshold> thr = vtkSmartPointer<vtkThreshold>::New();
thr->SetInputConnection(gf->GetOutputPort());

if( some_condition )
{
   thr->ThresholdByLower( some_value );
}

vtkSmartPointer<vtkThreshold> bthr = vtkSmartPointer<vtkThreshold>::New();
bthr->SetInputConnection( thr->GetOutputPort() );
bthr->ThresholdByLower( BAD_VALUE );

vtkSmartPointer<vtkDataSetSurfaceFilter> surfFilter =
vtkSmartPointer<vtkDataSetSurfaceFilter>::New();
surfFilter->SetInputConnection( bthr->GetOutputPort() );
...
...

How will 'thr' behave when 'some_condition' is false? Will there be any
thresholding? If so then what will be the threshold value? What values will
be passed to 'bthr'..??

I am asking this because, without

vtkSmartPointer<vtkThreshold> thr = vtkSmartPointer<vtkThreshold>::New();
thr->SetInputConnection(gf->GetOutputPort());

if( some_condition )
{
   thr->ThresholdByLower( some_value );
}

part of code, previously it was displaying correct output. After inserting
this code, I am getting blank output.. Output is to display filled contour
for a grid.

Thanks

Regards
Rakesh Patil
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