# Why is the circle divided into 4 pieces?

**URL:** <https://discourse.vtk.org/t/why-is-the-circle-divided-into-4-pieces/8776>\
**Category:** Development\
**Created:** [June 22, 2022, 4:41am UTC](https://discourse.vtk.org/t/why-is-the-circle-divided-into-4-pieces/8776 "2022-06-22T04:41:17Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![ldk7972](https://discourse.vtk.org/letter_avatar_proxy/v4/letter/l/9fc348/32.png) [@ldk7972](https://discourse.vtk.org/u/ldk7972)\
**Post date:** [June 22, 2022, 4:41am UTC](https://discourse.vtk.org/t/why-is-the-circle-divided-into-4-pieces/8776/1 "2022-06-22T04:41:17Z")

</div>

![원이아닌원](https://discourse.vtk.org/uploads/default/original/2X/7/713d8d5676d022d7261795fd040724c0ef8d8cd0.jpeg)

```
vtkNew<vtkRenderWindowInteractor> Interactor; 
m_pvtkImageViewer->SetupInteractor(Interactor);

vtkNew<vtkRegularPolygonSource> polygonSource;
polygonSource->SetNumberOfSides(360);
polygonSource->SetRadius(20);
polygonSource->SetNormal(0.0, 0.0, 1.0);
polygonSource->SetCenter(20, 20, 1);
polygonSource->SetGeneratePolygon(FALSE);
polygonSource->SetGeneratePolyline(TRUE);
polygonSource->Update(); 

vtkNew<vtkPolyDataMapper> mapper;
mapper->SetInputConnection(polygonSource->GetOutputPort());

vtkNew<vtkNamedColors> colors;
vtkNew<vtkActor> actor;
actor->SetMapper(mapper);

actor->GetProperty()->SetLineWidth(10.0);

actor->GetProperty()->ShadingOn();
actor->GetProperty()->SetPointSize(1);

actor->GetProperty()->SetColor(1.0, 0.2, 0.6);
actor->GetProperty()->SetOpacity(0.7); 

m_pvtkImageViewer->GetRenderer()->SetUseFXAA(TRUE);
m_pvtkImageViewer->GetRenderWindow()->SetMultiSamples(0); 

m_pvtkImageViewer->GetRenderer()->AddActor(actor); 

m_pvtkImageViewer->GetImageActor()->InterpolateOff();
m_pvtkImageViewer->GetRenderer()->ResetCamera();
m_pvtkImageViewer->GetRenderer()->SetBackground(40.0 / 255.0, 60.0 / 255.0, 90.0 / 255.0);
m_pvtkImageViewer->Render();

```

I wanted to draw a circle, but when I set the thickness, 4 pieces came out.  
Help me…