title: How to get faces and vertices from vtkVoxelContoursToSurfaceFilter?
body: <p>I am following the  ContoursToSurface (<a href="https://lorensen.github.io/VTKExamples/site/Cxx/PolyData/ContoursToSurface/" rel="nofollow noreferrer">https://lorensen.github.io/VTKExamples/site/Cxx/PolyData/ContoursToSurface/</a>) example from VTK website. My question is simply how to get the faces and vertices after vtkVoxelContoursToSurfaceFilter acts on the contours?</p>
  
  <p>The number of different elements (Poly,Verts,Pieces,Points, Lines and Cells) after transforming back the output of filter from ijk coordinate to world coordinate before visualizing:</p>
  
  <pre class="lang-cpp prettyprint-override"><code>std::cout &lt;&lt; "GetNumberOfPolys :" &lt;&lt; std::to_string( transformFilter-&gt;GetOutput(0)-&gt;GetNumberOfPolys()) &lt;&lt; std::endl;
  std::cout &lt;&lt; "GetNumberOfPieces :" &lt;&lt; std::to_string( transformFilter-&gt;GetOutput(0)-&gt;GetNumberOfPieces()) &lt;&lt; std::endl;
  std::cout &lt;&lt; "GetNumberOfLines :" &lt;&lt; std::to_string( transformFilter-&gt;GetOutput(0)-&gt;GetNumberOfLines()) &lt;&lt; std::endl;
  std::cout &lt;&lt; "GetNumberOfVerts :" &lt;&lt; std::to_string( transformFilter-&gt;GetOutput(0)-&gt;GetNumberOfVerts()) &lt;&lt; std::endl;
  std::cout &lt;&lt; "GetNumberOfPoints :" &lt;&lt; std::to_string( transformFilter-&gt;GetOutput(0)-&gt;GetNumberOfPoints()) &lt;&lt; std::endl;
  std::cout &lt;&lt; "GetNumberOfCells :" &lt;&lt; std::to_string( transformFilter-&gt;GetOutput(0)-&gt;GetNumberOfCells()) &lt;&lt; std::endl;
  </code></pre>
  
  <p>This outputs the following (which I was not expecting)?</p>
  
  <pre class="lang-cpp prettyprint-override"><code>GetNumberOfPolys :0
  GetNumberOfPieces :1
  GetNumberOfLines :0
  GetNumberOfVerts :0
  GetNumberOfPoints :0
  GetNumberOfCells :0
  </code></pre>