[vtkusers] vtkBooleanOperationPolyDataFilter with SetOperationToDifference operating on identical vtkPolyData

[Toby Rule]

Thanks for the vtkbool reference.  That might do the trick!

Toby

-----Original Message-----
From: Cory Quammen [mailto:cory.quammen at kitware.com] 
Sent: Friday, April 18, 2014 10:46 AM
To: Toby Rule
Cc: vtkusers at vtk.org
Subject: Re: [vtkusers] vtkBooleanOperationPolyDataFilter with SetOperationToDifference operating on identical vtkPolyData

It would be *possible* to do as a preprocessing step prior to the main algorithm, but as it exists now, the filter should fail miserably, I suspect.

Perhaps this filter by Ronald Römer would do the right thing in this case?

https://github.com/zippy84/vtkbool

Best,
Cory

On Thu, Apr 17, 2014 at 11:43 AM, Toby Rule <trule at ii-vi.com> wrote:
> Is there a way to set up a vtkBooleanOperationPolyDataFilter so that, 
> when it is used to take a boolean difference between identical 
> vtkPolyData, it will result in an empty vtkPolyData? For instance, if 
> I start with
>
>     vtkPolyData * output
>
> and do ...
>
>     vtkSmartPointer<vtkBooleanOperationPolyDataFilter> diffFilter =
>       vtkSmartPointer<vtkBooleanOperationPolyDataFilter>::New();
>     diffFilter->SetOperationToDifference();
>     diffFilter->SetInputData(0,output1);
>     diffFilter->SetInputData(1,output1); // set input and output to 
> same geometry
>
> ... the result of the diffFilter operation appears to be identical to output1. For my application, the result should be an empty set.
>
> According to this VTK Journal article http://www.vtkjournal.org/browse/publication/797 the algorithm assumes there are no coplanar triangles, so it may be that what I ask is impossible, and I need to look at a solid modeling library.
>
> Thanks,
>
> Toby
>
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