1. Start ParaView (see <link> for information on how to launch ParaView)

2. Create a Plot3D file reader by selecting PLOT3DReader from VTK -> Sources
   menu. Click Browse next to the XYZFileName entry and locate combxyz.bin
   in the ParaView data directory. Next, click Browse next to the QFileName
   entry and locate combq.bin in the data directory. Click accept.

   <outline.jpg>

3. Create a glyph filter by clicking the Glyph button on the toolbar.

   <toolbar-glyph.jpg>

4. Click Accept to generate glyph with default values: Glyphs are 
   three-dimensional arrows (determined by "Glyph Source"), they
   are oriented with the momentum vector (determined by the Orient
   check button and "Point Vectors" menu) and scaled with the density 
   function (determined by "Scale Mode"). Please note that this will
   generate 56x32x24 glyphs which, depending on your processor and 
   graphics card's performance might take some time. If you have a
   slow processor or graphics card, you might want to skip step 4
   and move on to step 7 (if you have already created the glyph filter 
   continue with step 5).

   <glyphs1.jpg>

5. You will notice that because of the large number of glyphs, it takes
   a long time to fully render the scene. However, unless your computer
   is old, it should be possible to interact with the scene with acceptable
   speeds. This is because ParaView uses LOD (Level of Detail) actors to
   achieve acceptable rendering times while the user is interacting with
   a scene. This is accomplished by reducing the detail (number of polygons)
   as the requested frame rate increases. The requested frame rate can
   be changed from the toolbar. Experiment with different frame rate
   settings.

   <framerate.jpg>

6. It is also possible to achieve better interactivity and a less cluttered
   picture by reducing the number of data points which are glyphed.
   First, remove the glyph filter by clicking Delete on the source notebook.


7. Next create a masking filter by selecting MaskPoints from then 
   VTK -> Filters menu. Set the OnRatio to 40. This is the ratio of the
   points retained: 1 out of every 40 points will be retained. Turn on
   random point selection by clicking on the Random checkbox. Click Accept.
   Note that the outline of the solution domain might disappear as a result
   of this action. You can turn it back on by going back to the Plot3D source
   (click on Plot3D1 in the Navigation window, switch to the display notebook
   and check the visibility option). Now, create a glyph filter. This time, 
   change the "Scale Mode" to Vector  so that glyphs are scaled by the  
   magnitude of the vectors. Reduce the  Scale Factor to 0.005 (otherwise 
   the arrows will be very large) and click Accept.

   <result.jpg>
   
   Note that since the problem geometry is represented by a structured
   grid, it is possible to sub-sample the points in a more appropriate
   way. You can use a structured grid extraction filter ( ExtactGrid 
   filter from VTK -> Filters -available only when a structured grid
   source is active- ) instead of masking points randomly. The extraction
   filter allows you sub-sample the grid by setting sampling rates in
   x, y and z directions. The following image was obtained by using
   an ExtractGrid filter with a VOI (volume of interest) of ((4,55),
   (3,31), (3,23)) and sampling rate of (3,3,3).

   <extract.jpg>