[vtkusers] How to measure the volume from the many objects separated

Cory Quammen cquammen at cs.unc.edu
Wed Feb 27 13:59:35 EST 2008

You could tetrahedralize the volume within isosurface and sum up the
volumes of the tetrahedra in the result. I believe the vtkDelaunay3D
won't do the job in this case because it ignores the surface
information in your isosurface, constructing a Delaunay
tetrahedralization from  just the point information. I have used the
TetGen library (http://tetgen.berlios.de/) to generate what's called a
constrained Delaunay tetrahedralization. This fills only the space
interior to your isosurface with tetrahedra. The only requirement is
that your isosurface has no holes, which is most like the case with
output from marching cubes (unless the isosurface intersects the edge
of the entire volume).

I have wrapped TetGen inside a VTK class to make it easy to use with
the output of things like the marching cubes filter. I could send it
to you, but you would have to set up a vtkLocal build, which may or
may not be something you want to do.

Hope that helps,

On Wed, Feb 27, 2008 at 1:10 PM, walmor godoi <wfisico at yahoo.com.br> wrote:
> Hi,
>  I need estimate the volume and area from a phantom (a acrylic cylinder with 12 holes in cylinder format too).
>  After the reconstruction by Marching Cubes of the phantom with 12 holes (cilinder format), successfully, i used thevtkMassProperties for measures of volume and surface area. But the volume and area was the extentof the entire cylinder which contains the twelve holes, i.e.,  vtkMassProperties just seeing the cylinder without the holes (I believe because theactors-holes should be targeted or labelled so they can beindependently measured and it will be the goal now).
>  Does anyone have an example of how to measure the volume from the many objects separated ?
>  ----------------------------------------------------------------------------------
>  Walmor Cardoso Godoi, M. Sc.
>  Curitiba - Paraná - Brazil
>  Msn: walmorgodoi at hotmail.com
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Cory Quammen
Department of Computer Science
University of North Carolina at Chapel Hill

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