[vtkusers] Interactivly changing isovalue using slider

[Gerrick Bivins]

Hi Divya,

I also found this a little "unintuitive". Even though you specify the same "contour index" in SetValue,

you also need to make sure you set  the number of contours to 1. Otherwise, the filter just continues to add them:

http://www.vtk.org/doc/nightly/html/classvtkContourFilter.html#a5485ad7720282f2001fa6443c303003a



Hopefully that helps.

Gerrick

________________________________
From: vtkusers [vtkusers-bounces at vtk.org] on behalf of Divya Rathore [divyarathore at gmail.com]
Sent: Wednesday, January 29, 2014 11:06 AM
To: vtkusers at vtk.org
Subject: [vtkusers] Interactivly changing isovalue using slider

Hi All,

I am trying to change the isovalue interactively in the medical2 sample. I am trying to use the 3D Slider example (http://www.vtk.org/Wiki/VTK/Examples/Cxx/Widgets/Slider) to do this.

I have modified the above class vtkSliderCallback as:

class vtkSliderCallback : public vtkCommand
{
public:
static vtkSliderCallback *New()
{
return new vtkSliderCallback;
}
virtual void Execute(vtkObject *caller, unsigned long, void*)
{
vtkSliderWidget *sliderWidget = reinterpret_cast<vtkSliderWidget*>(caller);
int value = static_cast<int>(static_cast<vtkSliderRepresentation *>(sliderWidget->GetRepresentation())->GetValue());
this->contourFilter->SetValue(0, value);
this->contourFilter->Update();
this->polyDataNormals->Update();
this->stripper->Update();
this->polyDataMapper->Update();
this->renderWindow->Render();
}
vtkSliderCallback():ImageActor(0)
{
contourFilter = NULL;
polyDataNormals = NULL;
stripper = NULL;
polyDataMapper = NULL;
renderWindow = NULL;
}
vtkContourFilter *contourFilter;
vtkPolyDataNormals *polyDataNormals;
vtkStripper *stripper;
vtkPolyDataMapper *polyDataMapper;
vtkRenderWindow* renderWindow;

};


main()
{

// read data
  // short data
  vtkSmartPointer<vtkImageReader> v16 = vtkSmartPointer<vtkImageReader>::New();
  v16->SetFileName(argv[2]);
  v16->SetFileDimensionality(3);
  v16->SetDataScalarTypeToUnsignedShort();
  v16->SetDataByteOrderToLittleEndian();
  v16->SetNumberOfScalarComponents(1);
  v16->SetDataExtent(0,width-1, 0,height-1, 0,depth-1);
  v16->SetDataSpacing (1.0, 1.0, 1.0);
  v16->Update();
  //..##

// An isosurface, or contour value of 500 is known to correspond to
// the skin of the patient. Once generated, a vtkPolyDataNormals
// filter is is used to create normals for smooth surface shading
// during rendering.  The triangle stripper is used to create triangle
// strips from the isosurface; these render much faster on may
// systems.
  vtkSmartPointer<vtkContourFilter> Extractor =
    vtkSmartPointer<vtkContourFilter>::New();
  Extractor->SetInputConnection( v16->GetOutputPort());
  Extractor->ReleaseDataFlagOn();
  Extractor->SetValue(0, 10240.0);
  Extractor->Update();

  vtkSmartPointer<vtkPolyDataNormals> Normals =
    vtkSmartPointer<vtkPolyDataNormals>::New();
  Normals->SetInputConnection(grainExtractor->GetOutputPort());
  Normals->ReleaseDataFlagOn();
  Normals->SetFeatureAngle(60.0);
  Normals->Update();

  vtkSmartPointer<vtkStripper> Stripper =
    vtkSmartPointer<vtkStripper>::New();
  Stripper->SetInputConnection(grainNormals->GetOutputPort());
  Stripper->ReleaseDataFlagOn();
  Stripper->Update();

  vtkSmartPointer<vtkPolyDataMapper> Mapper =
    vtkSmartPointer<vtkPolyDataMapper>::New();
  Mapper->SetInputConnection(grainStripper->GetOutputPort());
  Mapper->ReleaseDataFlagOn();
  Mapper->ScalarVisibilityOff();

  vtkSmartPointer<vtkActor> surface =
    vtkSmartPointer<vtkActor>::New();
  surface->SetMapper(grainMapper);
  surface->GetProperty()->SetDiffuseColor(.66, .92, .33);
  surface->GetProperty()->SetSpecular(.3);
  surface->GetProperty()->SetSpecularPower(20);
  surface->GetProperty()->SetOpacity(1.0);


// set up the slider
  vtkSmartPointer<vtkSliderCallback> callbackSlider = vtkSmartPointer<vtkSliderCallback>::New();
  callbackSlider->contourFilter = Extractor;
  callbackSlider->polyDataNormals = Normals;
  callbackSlider->stripper = Stripper;
  callbackSlider->polyDataMapper = Mapper;
  callbackSlider->renderWindow = renWin;

//..
// other aspects as covered in the above URL
//..

// Finally add observer
sliderWidgetSCP->AddObserver(vtkCommand::EndInteractionEvent, callbackSlider);

}



As such the interactivity pipeline is in place. But the problem is that on moving the slider the previous iso-values are not clearing and the surfaces keep on adding up (the shown surface keeps growing, obviously it all having the same color due to the call this->contourFilter->SetValue(0, value))

What am I missing here? I want just that iso-value to be shown that the slider reflects.

best regards,
Divya

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