[vtkusers] does returning "vtkPolyData" work?

[David Doria]

On Sun, Jan 3, 2010 at 5:11 PM, Aashish Chaudhary
<aashish.chaudhary at kitware.com> wrote:
> Zein,
>
> Use the smart pointers all the way (for return value and for the lvalue) if
> you want to use smart pointers like this.
>
> For some more information on smart pointers .. look here.
>
> http://www.vtk.org/Wiki/Smart_Pointers
>
> Hope I helped.
>
> ~Regards
>
>
> On Sun, Jan 3, 2010 at 11:40 AM, Zein Salah <zeinsalah at gmail.com> wrote:
>>
>> 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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>
>
> --
> | Aashish Chaudhary
> | R&D Engineer
> | Kitware Inc.
> | www.kitware.com

This little section is actually quite confusing:

http://www.vtk.org/Wiki/Smart_Pointers#Returning_a_Smart_Pointer

If the following is correct, I will update the page to only show this
and simply say "just do it this way":

----------
vtkSmartPointer<vtkPolyData> MyFunction()
{
  vtkSmartPointer<vtkPolyData> myObject = vtkSmartPointer<vtkPolyData>::New();
  return myObject;
}

And call the function using:
vtkSmartPointer<vtkPolyData> MyPolydata = MyFunction();
---------

Can someone verify this is how it should be done?

Thanks,

David