# Why the vtkSelectPolyData returns wrong area?

**URL:** https://discourse.vtk.org/t/why-the-vtkselectpolydata-returns-wrong-area/5041
**Category:** Support
**Created:** [January 21, 2021, 10:26am UTC](https://discourse.vtk.org/t/why-the-vtkselectpolydata-returns-wrong-area/5041 "2021-01-21T10:26:03Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![Jaafar\_Nasrabadi](https://discourse.vtk.org/user_avatar/discourse.vtk.org/jaafar_nasrabadi/32/1387_2.png) [@Jaafar\_Nasrabadi](https://discourse.vtk.org/u/Jaafar_Nasrabadi)
#### Post date: [January 21, 2021, 10:26am UTC](https://discourse.vtk.org/t/why-the-vtkselectpolydata-returns-wrong-area/5041/1 "2021-01-21T10:26:03Z")

</div>

Hi.  
I selected a region of a polydata by a loop of points and extract selected region inside the loop with vtkSelectPolyData and vtkClipPolyData but it contains extra points.  
sometimes vtkSelectPolyData can’t select area inside the loop and returns wrong area.  
Where are the problem?