[vtkusers] Re : vtkBooleanOperationPolyDataFilter: SetOperationToDifference gives me strange results

[Miguel Sotaquira]

Hi Cory,

Thanks for your answer. In the end I'm thinking of using
vtkKdTreePointLocator to iteratively find the points in mesh B present in
mesh A, and then vtkCleanPolyData to remove those points.

Thanks,
Miguel

On Thu, May 24, 2012 at 1:17 PM, Cory Quammen <cquammen at cs.unc.edu> wrote:

> The boolean operations are tailored to find the boundaries of volumes
> defined by boolean operations on the *volumes* defined by the input
> meshes. That's why the inputs are required to be manifold. In
> addition, the class assumes that any intersection between the two
> input poly datas can be described by a set of line segments. This
> makes breaking the input meshes into regions defining the union and
> intersection boundaries relatively easy. In your case, the
> intersection consists of a triangular mesh, and the boolean operation
> filter isn't able to handle that case.
>
> For the example you pose, perhaps you could compute the cell centers
> from your meshes and use a point locator to determine if a cell from
> one surface or the other is the only one present at a location?
>
> Cory
>
> On Thu, May 24, 2012 at 2:58 AM, Malsoaz James <jmalsoaz at yahoo.fr> wrote:
> > This thread may help
> > :
> http://vtk.1045678.n5.nabble.com/Holes-in-mesh-after-vtkBooleanOperationPolyDataFilter-td5713284.html
> >
> > ________________________________
> > De : Miguel Sotaquira <msotaquira at gmail.com>
> > À : vtkusers at vtk.org
> > Envoyé le : Jeudi 24 mai 2012 5h25
> > Objet : [vtkusers] vtkBooleanOperationPolyDataFilter:
> > SetOperationToDifference gives me strange results
> >
> > Hi everyone,
> >
> > I'm trying to compute an XOR boolean operation between two NON manifold
> > surfaces (see figure
> http://shareimage.org/images/3s5diyk1oypdib5fvx80.png).
> > The surface A is the white one (top panel of previous figure) and the
> > surface B is the red one (bottom panel). B is simply a region extracted
> from
> > A using vtkExtractPolyDataGeometry.
> >
> > Now I want to compute a boolean XOR between A and B in order to get C:
> the
> > green colored surface. I'm using vtkBooleanOperationPolyDataFilter:
> >
> > vtkSmartPointer<vtkBooleanOperationPolyDataFilter> boolean
> > = vtkSmartPointer<vtkBooleanOperationPolyDataFilter>::New();
> > boolean->SetOperationToDifference();
> > boolean->SetInput(0,meshA);
> > boolean->SetInput(1,meshB);
> > boolean->Update();
> >
> > vtkPolyData* meshC = boolean->GetOutput();
> >
> > However, when using this approach I obtain a surface like this (the blue
> > one): http://shareimage.org/images/gva77uyrmog4n2j1ndo.png;  that
> clearly is
> > not the expected XOR operation.
> >
> > I know I'm not using manifold surfaces (as explicitly required
> > by vtkBooleanOperationPolyDataFilter) so I don't know if that's why I'm
> > getting these results. If so, is there another way of computing this XOR
> > operation?
> >
> > Thanks,
> > Miguel
> >
> >
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>
>
> --
> Cory Quammen
> Research Associate
> Department of Computer Science
> The University of North Carolina at Chapel Hill
>
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