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Jan Ehrhardt wrote:
<blockquote TYPE=CITE>I have surface objects of anatomical tube-like structures
(e.g.
<br>vessels)
<br>How can I compute a central line (the skelett) of a
<br>surface object ?
<p>Thanks.
<p> Jan</blockquote>
<p><br>Jan,
<p>I think it is not a very simple problem. If your structure is a vessel,
I guess orthogonal sections are not exact circles and they are not even
exact ellipses. Therefore, the skeleton (in a morphological sense) is not
gonna be a line (it can be a "piece of surface", or several lines).
<br>You can have a look at some kind of "medial axis" or "core" (see "Computation
of Object Cores from grey-level images", B.S. Morse, PhD Thesis, University
of North Carolina at Chapel Hill, 1994), but this not a straightforward
implementation in your case
<p>If your surface is properly parameterised (i.e. one parameter r that
goes "along" the vessel, and one parameter s that goes "around" it, see
the figure below), you can get an approximation by computing for each value
of r the barycenter of the section described by s. You'll then have
a set of points which more or less describe some kind of "central line",
depending on the quality of your parameterisation.
<br>
<p><tt>----------------------</tt>
<br><tt> ^
-> r</tt>
<br><tt> |s</tt>
<br><tt>----------------------</tt><tt></tt>
<p>I guess that the problem is that it is not obvious to define what is
the "central line" of something which is not exactly a cylinder.
<p>- Olivier
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