[vtk-developers] Issue to get plane from vtkPlanes

[Laurent Chauvin]

Yes. This is how the 2nd signature work, but I was thinking the first one
was basically the same, returning a new vtkPlane* when you call it. But it's
not a new one, it seems to be the same everytime (this is what is explained
in the description in the header (explications that I missed) ).

Laurent.

On Tue, Jul 12, 2011 at 12:40 PM, David Cole <david.cole at kitware.com> wrote:

> On Tue, Jul 12, 2011 at 10:33 AM, Biddiscombe, John A. <biddisco at cscs.ch>
> wrote:
> > is really a question for the users list, but the answer is actually
> written
> > in the header file.
> >
> >
> >
> > if you look at the doc
> >
> >   // Description:
> >
> >   // Create and return a pointer to a vtkPlane object at the ith
> >
> >   // position. Asking for a plane outside the allowable range returns
> NULL.
> >
> >   // This method always returns the same object.
> >
> >   // Use GetPlane(int i, vtkPlane *plane) instead
> >
> >   vtkPlane *GetPlane(int i);
> >
> >   void GetPlane(int i, vtkPlane *plane);
> >
> >
> >
> > you can see that the same object is used every time and so your pointers
> are
> > the same. so use GetPlane(...) instead, where a new object is created for
> > you.
>
> I'm pretty sure to use that 2nd signature where you pass in a
> "vtkPlane *" that you have to create a vtkPlane object to pass in
> before you make the call. You create it, the call fills it in for you,
> then you delete it when you're done with it.
>
>
> >
> >
> >
> > you must delete the extra objects when you’re done with them.
> >
> >
> >
> > JB
> >
> >
> >
> > From: vtk-developers-bounces at vtk.org [mailto:
> vtk-developers-bounces at vtk.org]
> > On Behalf Of Laurent Chauvin
> > Sent: 12 July 2011 16:25
> > To: vtk-developers at vtk.org
> > Subject: [vtk-developers] Issue to get plane from vtkPlanes
> >
> >
> >
> > Hello,
> >
> > I was using vtkPlanes, and I needed to retrieve 2 planes (number 4 and
> 5).
> >
> > When I was using:
> >
> > planes->GetPlane(5) and planes->GetPlane(4)
> >
> > and using this as argument for clipping, like this:
> >
> > clip->SetClipFunction(planes->GetPlane(5));
> > clip2->SetClipFunction(planes->GetPlane(4));
> >
> > But, when I was not doing clip2, everything was working good, but after
> > adding clip2, my first clip changed and become the same as the clip2.
> >
> > So, I try this insted:
> >
> > vtkPlane* plane1 = vtkPlane::New();
> > planes->GetPlane(4, plane1);
> >
> > vtkPlane* plane2 = vtkPlane::New();
> > planes->GetPlane(5, plane2);
> >
> > clip->SetClipFunction(plane1);
> > clip2->SetClipFunction(plane2);
> >
> > And it works.
> > I don't really understand. Is there shared memory in these classes
> > (vtkPlanes, vtkClipPolyData) ?
> > I was thinking the vtkClipPolyData output was shared, so the clip2 write
> in
> > the same place than the clip, which could explain why they are the same
> > after second clipping.
> >
> > Thank you.
> > Laurent.
> >
> >
> > --
> >
> > Laurent Chauvin, MS
> >
> > Surgical Planning Laboratory, Radiology
> >
> > Brigham And Women's Hospital, Harvard Medical School
> >
> > http://wiki.ncigt.org/index.php/User:Lchauvin
> >
> >
> >
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>



-- 
Laurent Chauvin, MS
Surgical Planning Laboratory, Radiology
Brigham And Women's Hospital, Harvard Medical School
http://wiki.ncigt.org/index.php/User:Lchauvin
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