# A question about vtkOpenGLHardwareSelector::GeneratePolygonSelection
**URL:** https://discourse.vtk.org/t/a-question-about-vtkopenglhardwareselector-generatepolygonselection/9033
**Category:** Support
**Tags:** jobs
**Created:** [July 28, 2022, 8:57am UTC](https://discourse.vtk.org/t/a-question-about-vtkopenglhardwareselector-generatepolygonselection/9033 "2022-07-28T08:57:02Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@loufear](https://discourse.vtk.org/u/loufear)
#### Post date: [July 28, 2022, 8:57am UTC](https://discourse.vtk.org/t/a-question-about-vtkopenglhardwareselector-generatepolygonselection/9033/1 "2022-07-28T08:57:02Z")
I use this method to get the visible surface of the ticked polygon data, but the output of the result is weird It looks like a part is missing, hope for help,
auto selector = vtkSmartPointer::New();
selector-\>SetRenderer(this-\>m\_render);
const int\* wsize = this-\>m\_render-\>GetSize();
const int\* origin = this-\>m\_render-\>GetOrigin();
selector-\>SetArea(origin[0], origin[1], origin[0] + wsize[0] - 1, origin[1] + wsize[1] - 1);
selector-\>SetFieldAssociation(vtkDataObject::FIELD\_ASSOCIATION\_CELLS);
if (selector-\>CaptureBuffers())
{
auto sel = selector-\>GeneratePolygonSelection(polygon.data(), res\_pts.size());
```
auto extractSelection = vtkSmartPointer::New();
extractSelection->SetInputData(0, this->m_poly_data);
extractSelection->SetInputData(1, sel);
extractSelection->Update();
```
}
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### Author:  [@loufear](https://discourse.vtk.org/u/loufear)
#### Post date: [July 28, 2022, 8:59am UTC](https://discourse.vtk.org/t/a-question-about-vtkopenglhardwareselector-generatepolygonselection/9033/2 "2022-07-28T08:59:03Z")
The polygon data is the convex hull from opencv The point set used is the trajectory of the mouse
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### Author:  [@loufear](https://discourse.vtk.org/u/loufear)
#### Post date: [July 28, 2022, 9:04am UTC](https://discourse.vtk.org/t/a-question-about-vtkopenglhardwareselector-generatepolygonselection/9033/3 "2022-07-28T09:04:12Z")
[Rendering/Core/Testing/Cxx/TestPolygonSelection.cxx · master · VTK / VTK · GitLab (kitware.com)](https://gitlab.kitware.com/vtk/vtk/-/blob/master/Rendering/Core/Testing/Cxx/TestPolygonSelection.cxx#L132) This is my reference
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### Author:  [@yangyang117](https://discourse.vtk.org/u/yangyang117)
#### Post date: [December 17, 2023, 1:44am UTC](https://discourse.vtk.org/t/a-question-about-vtkopenglhardwareselector-generatepolygonselection/9033/4 "2023-12-17T01:44:15Z")
Hi, Im using the python code for the selection.
I see it need to translate the address of data and the lenth of data in using `hardSel->GeneratePolygonSelection`
But in Python, it cannot translate the data’s address. Is there any way to fix it? or other api?