title: what is the difference in .SetInputConnection() and .SetInput()
body: <p>I was learning vtk on <a href="http://www.uppmax.uu.se/docs/w/index.php/How_to_Read_vtk_Files" rel="nofollow">http://www.uppmax.uu.se/docs/w/index.php/How_to_Read_vtk_Files</a>
  with this example.</p>
  
  <p>I found there is no difference when using </p>
  
  <pre><code>arrowGlyph.SetInput(reader.GetOutput())
  </code></pre>
  
  <p>or   </p>
  
  <pre><code>arrowGlyph.SetInputConnection(reader.GetOutputPort())
  </code></pre>
  
  <p>I know that Getoutput() gives you a vtkPolyData and GetOutputPort() gives you a vtkAlgorithmOuPut. But I don't know what is going on under the hood. Can they be used interchangeably?</p>
  
  <p>(my vtk version is 5.4)</p>