[vtkusers] questions about vtk Marching Square filter

John Biddiscombe jbiddiscombe at skippingmouse.co.uk
Mon Oct 21 18:19:22 EDT 2002

Try vtkStripper to join line segments into a polygon.


----- Original Message -----
From: "Zhan Zhang" <ZhangZ at mail.nlm.nih.gov>
To: <vtkusers at public.kitware.com>
Sent: Monday, October 21, 2002 10:14 PM
Subject: [vtkusers] questions about vtk Marching Square filter

> Hi,
> I have some questions about the vtk Marching Squares filter.
> Suppose I have a two-dimensional binary image, in which there is a
> donut-like object. If I use marching square to extract the shape
> boundary, I should get two circles (the inner and outer boundaries of
> the donut-like object). I find that in the output file (vtk Poly Data
> file) of the vtk marching square filter, the Cells Part are only line
> cells---no polygons. In fact, what I am most interested in is the
> connectivity lists of the points on these two boundaries, so I have to
> generate these two point-lists (a point-list here represents one
> circular boundary) by myself.
> 1) Can anyone tell me whether VTK marching square provides such
> functionality?
> 2) Suppose I have to generate such lists by myself strictly according
> to the point connectivity indirectly given to me in the Line Cells Part
> of the vtk Poly Data file, or suppose vtk can do this, my next question
> is: suppose that in the binary image I traverse the calculated point
> list representing the outer circle and that I look at my right hand side
> and I always see "black", if I do the same thing on the second point
> list representing the inner circle, will I always see "black" if
> look at my right hand side?
> Hopefully I can get the answers. Thanks for reading this email.
> Zhan
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