[vtk-developers] Generated normals not present in the polydata from unknown reason.

Bill Lorensen bill.lorensen at gmail.com
Fri Apr 20 10:34:17 EDT 2012


Oops...
Try
normalGenerator->Update();
 before
polydata = normalGenerator->GetOutput();


On Fri, Apr 20, 2012 at 10:33 AM, Bill Lorensen <bill.lorensen at gmail.com> wrote:
> Try
> normalGenerator-Update();
> before
> polydata = normalGenerator->GetOutput();
>
>
> On Fri, Apr 20, 2012 at 10:30 AM, Jana Sefcikova <neollie at gmail.com> wrote:
>> Dear Users,
>> I tested vtk example PolyDataExtractNormals
>> (http://www.vtk.org/Wiki/VTK/Examples/Cxx/PolyData/PolyDataExtractNormals)
>> code that tries to detect whether normals are present in input polydata
>> structure and if not it will generate them. I made small change to code  at
>> the end of the main function in order to run TestPointNormal twice so I have
>> :
>>
>>   std::cout << "PolyData address: " << polydata << std::endl;
>>   TestPointNormals(polydata);
>>
>>   TestPointNormals(polydata);
>>
>> I expected that after first round the polydata will be changed and will
>> contain new array for "Normals"  because output of normal generator is
>> assigned to input polydata in the first round / polydata =
>> normalGenerator->GetOutput(); /
>> so second  test round should pass directly without normal generation.
>> But after the firt test, polydata normals are not present any more so second
>> Test generate them  again .
>> So my question is : Why normals dissapeared ?
>> The same confusion for me occured when I enabled splitting on normal
>> generator (normalGenerator->SetSplitting(1);).  Inside first
>> TestPointNormals polydata had more points as before at the end (due to
>> splitting), but second test again work on likely unchanged polydata.
>>
>> Why two functions working on the same pointer that is changed inside each
>> call looks unchanged ?
>>
>> Thanks for any advice.
>>
>>
>>
>>
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>
>
>
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