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We have had Bezier curves in KrackPlot for years.  It is definitely a good
way to go for flexibly making curves around all kinds of objects.  The one
disadvantage is that you have to make the curves yourself - there is no
simulated annealing, spring embedder, or MDS function that will do it for
you.  You make curves on the screen by dragging the bezier points around
until the curve looks good.  In KrackPlot, you have two bezier points for
each line, allowing you to create complex curves.  It is fairly easy to do,
but it is time consuming if you want a lot of curves, like Lombardi has.

-David

--On Wednesday, November 19, 2003 2:31 PM +0000 Perry Dyball
<[log in to unmask]> wrote:

> *****  To join INSNA, visit http://www.sfu.ca/~insna/  *****
>
> Hi All
>
> We are currently working on implementing Bezier Curves in our product
> antology when actors are linked for more than one type of relation, as
> this is an elegant solution to avoid straight lines overlaying one
> another. When a point is used to represent a node rather than a block,
> there is a very small area to bind edges to the node, and hence straight
> lines will always draw over the top of one another, effectively 'hiding'
> the fact that multiple relations exist. We have thought about using
> composite line styles, call outs etc in these circumstances, but Bezier
> Curves give by far the best result.
>
> If anyone has taken any other approaches, I'd be interested to hear your
> views.
>
> However, we think that it will be quite sometime before we see automated
> generation of graphs of the beauty Lombardi produced by hand from his
> data - unless anyone knows any different of course!
>
> Perry Dyball
> CakeHouse Systems
>
> T.      +44 (0)207 917 1829
> M.      +44 (0)780 329 3630
> F.      +44 (0)870 052 3440
> E.      mailto:[log in to unmask]
> A.      212 Piccadilly, London W1J 9HG
> W.      http://www.cakehouse.co.uk
>
> -----Original Message-----
> From: Jim W Lai [mailto:[log in to unmask]]
> Sent: 18 November 2003 17:23
> To: [log in to unmask]
> Subject: Re: Lombardi edges
>
>
> *****  To join INSNA, visit http://www.sfu.ca/~insna/  *****
>
> On Mon, 17 Nov 2003, Peter Simon wrote:
>> We could have pseudo-Lombardi edges--curved in some fashion rather than
> dead
>> straight.
>
> Splines have been extensively studied and used in the computer graphics
> field.
> That would be my recommendation for a starting point, as it were.
>
> For instance, Google also turned up this fairly quickly.
> http://www.research.att.com/areas/visualization/papers_videos/ofullindex.
> htm l
> "Path Router (MPG - 4.3 MB)
> "Illustrates a technique for routing a smooth curve between two points
> while avoiding intervening objects. The technique and its related
> aesthetics were designed for drawing edges of graphs."
>
> Jim
>
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------------------------------
David Krackhardt, Professor of Organizations, Editor of JoSS
Carnegie Mellon University
http://www.andrew.cmu.edu/~krack
JoSS: <http://www2.heinz.cmu.edu/project/INSNA/joss/>
           (Erdos#=2)

_____________________________________________________________________
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