[vtkusers] Re : Holes in mesh after vtkBooleanOperationPolyDataFilter

[Cory Quammen]

There's a known problem when vertices on one of the input surfaces are
within epsilon of a surface-to-surface intersection. It's on my to do
list to make this more robust.

Thank you for providing another example for me to test.

Thanks,
Cory

On Tue, May 22, 2012 at 9:02 AM, Malsoaz James <jmalsoaz at yahoo.fr> wrote:
> Thank you,
>
> I'm gonna try this solution.
>
> Is this problem due to the implementation of the algorithm to compute the
> boolean operation ?
>
> I'm a bit confused, because the holes doesn't appear in a place where there
> are intersections or unions.
>
> I have been trying to use this website : http://evanw.github.com/csg.js/ to
> test another implentation of the CSG and it works even with parallel
> surfaces.
> You can try the following in the text box at the end of the page (note that
> the page requires WebGL) :
>
> var a = CSG.cylinder({radius:0.2, center:[0, 0, 0]});
> var b = CSG.cube({radius:[1, 0.5, 0.2], center:[0, 0, 0]});
> var c = CSG.cylinder({radius:0.2, start: [-1, -1, 0], end: [-1, 1, 0]});
> return a.union(b).union(c);
>
> Best.
>
> ________________________________
> De : Bryn Lloyd <lloyd at itis.ethz.ch>
> À : vtkusers at vtk.org
> Envoyé le : Mardi 22 mai 2012 14h05
> Objet : Re: [vtkusers] Holes in mesh after vtkBooleanOperationPolyDataFilter
>
> The boolean operations are not robust for parallel surfaces.
>
> One way to try to resolve the problem is to move the objects by some small
> delta before applying the boolean operation.
>
>
> On 5/22/2012 11:15 AM, Malsoaz James wrote:
>
> Hi VTK users,
>
> I'm using the vtkBooleanOperationPolyDataFilter to apply boolean operations
> to polydata. Unfortunately, I got unexpected results (holes in the mesh).
>
> You can see here http://www.hostingpics.net/viewer.php?id=210273error.png an
> example.
> I'm creating a cylinder, then I'm adding a cube and finally I'm adding
> another cylinder. The holes appear with the last operation.
>
>
> Can someone explain me the reason(s) of these results ?
>
> Here are my source code :
> vtkCylinderSource * cylinder1 = vtkCylinderSource::New();
> cylinder1->SetCenter(0, 10, 0);
> cylinder1->SetHeight(50);
> cylinder1->SetRadius(5);
> cylinder1->SetResolution(100);
> cylinder1->Update();
>
> vtkTriangleFilter * cylinder1Triangle = vtkTriangleFilter::New();
> cylinder1Triangle->SetInput(cylinder1->GetOutput());
> cylinder1Triangle->Update();
>
> cylinder1->Delete();
>
> vtkCubeSource * cube = vtkCubeSource::New();
> cube->SetCenter(0, 10, 0);
> cube->SetXLength(50);
> cube->SetYLength(20);
> cube->SetZLength(10);
> cube->Update();
>
> vtkTriangleFilter *cubeTriangle = vtkTriangleFilter::New();
> cubeTriangle->SetInput(cube->GetOutput());
> cubeTriangle->Update();
>
> cube->Delete();
>
> vtkCylinderSource * cylinder2 = vtkCylinderSource::New();
> cylinder2->SetCenter(-25, 15, 0);
> cylinder2->SetHeight(30);
> cylinder2->SetRadius(3);
> cylinder2->SetResolution(100);
> cylinder2->Update();
>
> vtkTriangleFilter * cylinder2Triangle = vtkTriangleFilter::New();
> cylinder2Triangle->SetInput(cylinder2->GetOutput());
> cylinder2Triangle->Update();
>
> cylinder2->Delete();
>
> vtkBooleanOperationPolyDataFilter * add1 =
> vtkBooleanOperationPolyDataFilter::New();
> add1->SetOperationToUnion();
> add1->SetInput(0, cylinder1Triangle->GetOutput());
> add1->SetInput(1, cubeTriangle->GetOutput());
> add1->Update();
>
> cubeTriangle->Delete();
> cylinder1Triangle->Delete();
>
> vtkBooleanOperationPolyDataFilter * add =
> vtkBooleanOperationPolyDataFilter::New();
> add->SetOperationToUnion();
> add->SetInput(0, add1->GetOutput());
> add->SetInput(1, cylinder2Triangle->GetOutput());
> add->Update();
>
> add1->Delete();
> cylinder2Triangle->Delete();
>
> Am I doing something wrong in the use of vtkBooleanOperationPolyDataFilter ?
>
> Thank you.
> Best
>
>
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-- 
Cory Quammen
Research Associate
Department of Computer Science
The University of North Carolina at Chapel Hill