🚀 go-pugleaf

Hedgehog has a number of limitations, such as not being able to
conveniently place arrows at the exact positions of the original data
(even if it is uniform).  There also seem to be an unfortunate lower
limit on the vector scale.

Therefore, when recently faced with the problem of displaying 2-D vector
fields myself, I found the 'node' option in ucd hog module more appropriate. 
This draws arrows at the position of the input data points.
I have a short FORTRAN program to convert an irregular 2-D field of 
2-D vector components into an ASCII ucd file (using point elements
with a 3-D vector at each point).  It is not packaged for public
consumption, but I will mail it to anyone who wants it.

I was not completely satisfied with the result from ucd hog, in that
it could produce colour-coded arrows of a constant length, or white
arrows with a length proportional to the vector magnitude, but not
coloured arrows with a length proportional to the vector magnitude.

A useful addition to AVS would be hedgehog or ucd hog-like modules
(that is, modules that provide 'glyphs', such as arrows, at an 
arbitrary set of input data points) that provide for more flexibility:

 - provide direct support for 2-D fields
 - provide direct support for rectilinear, curvilinear and scatter data
 - accept an input vector field to provide direction information
 - accept an input scalar field to provide scaling information (not
   necessarily proportional to the magnitude of the vector field).
 - colour the glyph according to yet another field.
-- 
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Doug S. Phillips
Academic Computing Services, The University of Calgary
Internet: phillips@acs.ucalgary.ca         Telephone: (403) 220-8445