Alan Norton <alan@ucar.edu>
Interaction Technique 4:
Use planar probe for visual flow seed placement 
¥Useful to place flow seeds based on local data values
¥Planar probe provides cursor for precise placement in 3D
¥Field lines are immediately reconstructed as seeds are specified
Click to launch 8spot3dMerged.vss
maximize
Then load 8spot3dMerged.vdf
Click on probe mode, enable.
Note that vertical vorticity is shown.
Enable Flow, (and DVR).
Insert seeds at highest vorticity