[vtkusers] vtkImageDataGeometryFilter problem

Kim Rosenbohm kim.rosenbohm at posteo.de
Wed Aug 6 12:25:35 EDT 2014

Answering my own question here:

Apparently "ThresholdValueOn()" resolves to a Macro that takes a bool 
and sets the threshold value to the value "true" aka 1.
Really misleading. Is this a bug or Feature?! The documentation lacks 
there. At least tell me != 0 is on (besides that I might like to use 0 
as an actual threshold...)

Please forgive my rant, but I notice the problem throughout VTK with 
the C++ interface:

* Just take a look a "vtkCubeAxesActor". Theres such a load of 
functions that are basically "Set"/"On"/"Off":
"SetXAxisVisibility(int)" <- Why an int?!
"XAxisVisibilityOn()/Off()" <- You've now tripled the functions...
Why not instead a simple "SetXAxisVisibility(bool)"?! ...as in turn 
there actually IS only one "Get"-function...

* There's functions that take an int as a parameter, but actually 
expect an enum, e.g. "vtkCubeAxisActor::SetTickLocation(int)"
There's no proper way of telling which are the expected input values. 
Why not use an actual enum?!

* vtkImageData has "SetDimensions" marked as deprecated, but 
"SetExtent" uses width-1, height-1, plane-1...
This is IMAGE data. If you actually USE it for images you now always 
have to do a +1 or -1...

Just my 50ct about the library. My first 2-3 weeks have been pretty 

Best Regards,


Am 05.08.2014 14:28 schrieb Kim Rosenbohm:

> Hi All.
> Though nobody responded to my previous question, I'll try again with a
> different problem:
> I have a pipeline for masking out areas in a 2D image and turning the
> image data into a 3D surface:
> ...
> vtkSmartPointer< vtkImageResample > m_surfaceResampled;
> vtkSmartPointer< vtkImageResample > m_maskResampled;
> vtkSmartPointer< vtkImageMask > m_maskMask;
> vtkSmartPointer< vtkImageDataGeometryFilter > m_surfaceGeoFilter;
> vtkSmartPointer< vtkWarpScalar > m_surfaceWarpFilter;
> //use a vtkImageMask to remove masked-out stuff from an image
> m_maskMask->SetInputConnection(0, 
> m_surfaceResampled->GetOutputPort());
> m_maskMask->SetInputConnection(1, m_maskResampled->GetOutputPort());
> m_maskMask->SetMaskedOutputValue(-10000);
> //m_maskMask->SetMaskAlpha(0.0);
> //setup filter creating geometry from image/height data
> m_surfaceGeoFilter->SetInputConnection(m_maskMask->GetOutputPort());
> //setup masking out of cells marked in mask
> m_surfaceGeoFilter->ThresholdCellsOn();
> m_surfaceGeoFilter->ThresholdValueOn();
> //pass geometry to scale surface z-axis height
> m_surfaceWarpFilter->SetScaleFactor(1.0);
> ...
> This works ok for positive values in m_surfaceResampled, but not if I
> only have negative values there.
> Then I get no surface at all... Why?
> Additionally an eleborate explanation of what ThresholdCELLS and
> ThresholdVALUE do
> and how they interact would be nice. The documentation is not 
> dummy-proof
> enough for me there...
> Best Regards,
> Kim
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Kim Rosenbohm, Barfüßerstr. 7, 37073 Göttingen, 0163/8723172

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