Hi Antonio,<br /><br />
I've written a compilable example, which demonstrates converting an vtkImageData object to vtkPolyData is working properly:<br />

<pre>#<span style=' color: Blue;'>include</span> &lt;vtkVersion.h&gt;
#<span style=' color: Blue;'>include</span> &lt;vtkPolyDataMapper.h&gt;
#<span style=' color: Blue;'>include</span> &lt;vtkActor.h&gt;
#<span style=' color: Blue;'>include</span> &lt;vtkRenderWindow.h&gt;
#<span style=' color: Blue;'>include</span> &lt;vtkRenderer.h&gt;
#<span style=' color: Blue;'>include</span> &lt;vtkRenderWindowInteractor.h&gt;
#<span style=' color: Blue;'>include</span> &lt;vtkInteractorStyleUser.h&gt;
#<span style=' color: Blue;'>include</span> &lt;vtkSmartPointer.h&gt;
#<span style=' color: Blue;'>include</span> <span style=' color: Maroon;'>"vtkVolume16Reader.h"</span>
#<span style=' color: Blue;'>include</span> <span style=' color: Maroon;'>"vtkImageData.h"</span>
#<span style=' color: Blue;'>include</span> <span style=' color: Maroon;'>"vtkImageDataGeometryFilter.h"</span>

<span style=' color: Blue;'>int</span> main(<span style=' color: Blue;'>int</span>, <span style=' color: Blue;'>char</span> *[])
{

  vtkSmartPointer&lt;vtkVolume16Reader&gt; v16 = vtkSmartPointer&lt;vtkVolume16Reader&gt;::New();
  v16-&gt;SetDataDimensions(<span style=' color: Maroon;'>64</span>, <span style=' color: Maroon;'>64</span>); 

  v16-&gt;GetOutput()-&gt;SetOrigin(<span style=' color: Maroon;'>0</span><span style=' color: Maroon;'>.0</span>, <span style=' color: Maroon;'>0</span><span style=' color: Maroon;'>.0</span>, <span style=' color: Maroon;'>0</span><span style=' color: Maroon;'>.0</span>);
  v16-&gt;SetDataByteOrderToLittleEndian();
  v16-&gt;SetFilePrefix(<span style=' color: Maroon;'>"c:\\vtk\\vtkdata-5.8.0\\Data\\headsq\\quarter"</span>);
  v16-&gt;SetImageRange(<span style=' color: Maroon;'>1</span>, <span style=' color: Maroon;'>93</span>);
  v16-&gt;SetDataSpacing(<span style=' color: Maroon;'>3</span><span style=' color: Maroon;'>.2</span>, <span style=' color: Maroon;'>3</span><span style=' color: Maroon;'>.2</span>, <span style=' color: Maroon;'>1</span><span style=' color: Maroon;'>.5</span>);
  v16-&gt;Update();


  vtkImageData* imageData = v16-&gt;GetOutput();
  vtkSmartPointer&lt;vtkImageDataGeometryFilter&gt; filter = vtkSmartPointer&lt;vtkImageDataGeometryFilter&gt;::New();
  filter-&gt;SetInput(imageData);
  vtkSmartPointer&lt;vtkPolyDataMapper&gt; polyDataMapper = vtkSmartPointer&lt;vtkPolyDataMapper&gt;::New();
  polyDataMapper-&gt;SetInputConnection(filter-&gt;GetOutputPort());
  vtkSmartPointer&lt;vtkActor&gt; polyActor = vtkSmartPointer&lt;vtkActor&gt;::New();
  polyActor-&gt;SetMapper(polyDataMapper);
  <span style=' color: Green;'>// get a reference to the renderwindow of our renderWindowControl1</span>

  <span style=' color: Green;'>// Visualize</span>
  vtkSmartPointer&lt;vtkRenderer&gt; renderer =
    vtkSmartPointer&lt;vtkRenderer&gt;::New();
  vtkSmartPointer&lt;vtkRenderWindow&gt; renderWindow =
    vtkSmartPointer&lt;vtkRenderWindow&gt;::New();
  renderWindow-&gt;AddRenderer(renderer);
  vtkSmartPointer&lt;vtkRenderWindowInteractor&gt; interactor =
    vtkSmartPointer&lt;vtkRenderWindowInteractor&gt;::New();
  interactor-&gt;SetRenderWindow(renderWindow);

  renderer-&gt;AddActor(polyActor);
  renderWindow-&gt;SetSize(<span style=' color: Maroon;'>500</span>,<span style=' color: Maroon;'>500</span>);
  renderWindow-&gt;Render();
  renderWindow-&gt;Render();
  interactor-&gt;Start();
 
  <span style=' color: Blue;'>return</span> EXIT_SUCCESS;
}
</pre>

Maybe you will provide us with a full compilable small example demostrating the problem.
<br /><br />
best regards<br />
Jochen
        
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