title: store heterogeneous elements
body: <p>I would like to generate output files to subsequently visualize in Paraview. I will have:</p>
  <ul>
  <li>polygons (with scalar attributes)</li>
  <li>lines (with scalar attributes)</li>
  <li>data on structured grids</li>
  </ul>
  <p>In Paraview, I want to visualize all of them concurrently. For each class (e.g. polygon, lines), the color code will represent the individual attribute value.</p>
  <p>Question: do I have to generate one file per class, i.e. one file for the polygons and its attributes, one file for the lines and its attributes, and one file for the grid data, and assemble the 'full picture' manually in Paraview?</p>
  <p>Or is there a way to store everything in one single file?</p>