[vtkusers] does returning "vtkPolyData" work?

[Zein Salah]

Hello everybody,

I used smart pointers everywhere (return value, the lvalue) and it worked
as supposed to be.

Many Thanks,
Zein

@Rocco: Vielen Dank :).

On Mon, Jan 4, 2010 at 8:55 AM, Rocco Gasteiger <post at rocco-gasteiger.de> wrote:
> Hello Zein,
>
> I have two assumptions according to your smart pointer usage (I'm not very
> familiar with them until yet):
>
> 1. Maybe your polydata-pointer "polyData" is not valid outside of your
> function " MyClass::GenerateCont(...)". Your solution could be in returning
> "cutter->GetOutput()" directly instead of " vtkSmartPointer<vtkPolyData>
> polyData = cutter->GetOutput(); return polyData;"
>
> 2. According to this VTK-Documentation:
> http://www.vtk.org/Wiki/Smart_Pointers, the return type of your function
> could not be correct. Maybe you can try "vtkSmartPointer<vtkPolyData>
> MyClass::GenerateCont(...)" instead, additionally with "return
> cutter->GetOutput();" (like above) in combination with
> "vtkSmartPointer<vtkPolyData> MyPolydata = MyClass::GenerateCont(..)".
>
> I hope this gives you a little help.
>
> Best regards, Rocco
>
>
> -----Original Message-----
> From: vtkusers-bounces at vtk.org [mailto:vtkusers-bounces at vtk.org] On Behalf
> Of Zein Salah
> Sent: Sunday, January 03, 2010 5:41 PM
> To: vtkusers at vtk.org
> Subject: [vtkusers] does returning "vtkPolyData" work?
>
> Hallo ,
> In my class, I have a function that SHOULD return a vtkPolyData, which is
> the result of a vtkCutter, as shown below:
>
>
> vtkPolyData* MyClass::GenerateCont(double cntr[], double nrml[])
> {
>
>    vtkSmartPointer<vtkPlane> plane = vtkSmartPointer<vtkPlane>::New();
>    plane->SetOrigin(cntr[0], cntr[1], cntr[2]);
>    plane->SetNormal(nrml[0], nrml[1], nrml[2]);
>
>    vtkSmartPointer<vtkCutter> cutter = vtkSmartPointer<vtkCutter>::New();
>
>    cutter->SetInput(....); // some input vtkpolydata
>    cutter->SetCutFunction(plane);
>    cutter->Update();
>
>
>    vtkSmartPointer<vtkPolyData> polyData = cutter->GetOutput();
>    return polyData;
> }
>
>
> Now I have an array of struct, cArray, where one field of the struct is of
> type vtkPolyData*. When I call the GenerateCont function on the elements
> of the array, as follows
>
>
> for (int i= 0; i<num; i++) {
>     double       cntr[3];      cntr[0] = ...;     cntr[1] = ...;
>      cntr[2] = ...;
>     double       zdir[3];      zdir[0] = ...;            zdir[1] =
> ...;             zdir[2] = ...;
>
>     cArray[i].polyData = GenerateCont(cntr, zdir);
> }
>
> I noticed that the cArray is not updated. I.e. calling function GenerateCont
> does not return the supposed vtkPolyData. By testing whether the function
> GenerateCont works itself, I found that is the vtkCutter generates the
> output as required, only the output value is not returned.
>
> What is wrong I am doing? Is returning a vtkPolyData semantically wrong?
>
>
> Much thanks,
> Zein
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