Editing Vtk/Quadric (section)

===vtkContourFilter===
As is explained at the top of p. 78 of the [http://www.kitware.com/products/books/vtkguide.html ''VTK User's Guide''], five different contours &#8212; that is, five different surfaces differentiated from one another by color &#8212; have been drawn.  The ''specific'' set of surfaces has been specified via the "GenerateValues" method inside the vtkContourFilter module.  Clicking on (''i.e.,'' highlighting) the vtkContourFilter module in the VisTrails workflow reveals that three numbers have been specified:
* Two floating-point numbers identify the "scalar range" &#8212; in the default case, the specified range is <math>0.0 \rightarrow 1.2</math>;
* The single integer identifies the "number of contours to be generated in the range (end values inclusive).

We conclude that the five separately colored "surfaces" correspond to contours for which the function, <math>~F_0(x,y,z)</math>, is constant and has the following values:
<table border="1" cellpadding="5" align="center">
<tr>
  <th align="right">Contour Color:</th>
  <td align="center">red</td>
  <td align="center">yellow</td>
  <td align="center">green</td>
  <td align="center">light blue</td>
  <td align="center">dark blue</td>
</tr>
<tr>
  <th align="right">Associated Scalar Value:</th>
  <td align="center">0.0</td>
  <td align="center">0.3</td>
  <td align="center">0.6</td>
  <td align="center">0.9</td>
  <td align="center">1.2</td>
</tr>
</table>