Re: [Update REQ 6717]: Geomview

[Stuart Levy <slevy at geom.umn.edu>]

> I just started using Geomview and think it's a great piece of software!

Thanks!  That's always nice to hear...

> I
> do have a question, and hope this is the right place to send my questions.
> I read in some geometry as an OFF file and displayed it. The geometry is a
> mesh of triangles representing an anatomical structure which I am
> interested in for my research. I wish to extract and save the contour
> formed by the intersection of this geometry and the surface;

Which surface?

> the contour
> should be represented as a polyline. Is this task possible in Geomview?

It depends:
  If the surface you mean is, say, a simple plane -- sort of a virtual
  microtome for your anatomical structure -- then yes, you can
  do something like this using "clip" (command-line program) or "Ginsu"
  (interactive module).  Then, I believe "bdy" (Boundary) could be used
  to trace an outline of a clipped edge.  (You could also use "clip"
  to extract a thin slice between two parallel planes separated by a short
  distance, though this would yield a collection of polygons rather than
  a polyline.)

  If you're trying to find the intersection of two arbitrary surfaces,
  then there's no tool provided for doing that that's packaged with geomview.

However, I have written a program for another project that does 
most of the necessary work: it takes a triangulated OFF object and
finds all self-intersections, so you could combine the two surfaces
into one OFF file and run it.  Its output is currently an unordered
list of fragments of the self-intersection curve(s); I have other code
which sorts these out into connected arcs and loops, though it doesn't
currently write its results to a file.  If this is the kind of thing you need,
let me know and I can package it up.

  Stuart Levy





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