_ptpro;
_ptpro->SetLineWidth(5);
_ptpro->SetColor(1.0, 1.0, 0);
_ptpro->SetOpacity(0.4);
_ptpro->SetPointSize(5);
m_pDisplayActor->SetProperty(_ptpro);
m_pDisplayMapper->SetInputData(m_pPolygonTrack);
m_pDisplayActor->SetMapper(m_pDisplayMapper);
m_pTitleRenderer->AddActor(m_pDisplayActor);
m_pRenderWnd->Render();
m_nPointCount++;
```
Thanks for any advice!!!
---
### Author:  [@Hedwig\_Huang](https://discourse.vtk.org/u/Hedwig_Huang)
#### Post date: [January 31, 2024, 12:43am UTC](https://discourse.vtk.org/t/delete-the-overlapping-of-the-same-polygon-polydata/13180/2 "2024-01-31T00:43:50Z")
@dgobbi
Hi, Mr!
I notice that you had given some useful advice in the post([How to only render one vtkRender in vtkRenderWindow with two vtkRenders - #8 by Pisces2018](https://discourse.vtk.org/t/how-to-only-render-one-vtkrender-in-vtkrenderwindow-with-two-vtkrenders/11425/8)) Could you please give me some help about this problem?
Great thanks!
---
### Author:  [@dgobbi](https://discourse.vtk.org/u/dgobbi)
#### Post date: [January 31, 2024, 3:33am UTC](https://discourse.vtk.org/t/delete-the-overlapping-of-the-same-polygon-polydata/13180/3 "2024-01-31T03:33:04Z")
First thing is, always triangulate the track to make the polygon.
```c++
track->SetPoints(m_pPoints);
track->SetLines(m_pDisplayPlane);
auto segments = vtkSmartPointer::New();
segments->SetInputData(track);
segments->Update();
auto triangulator = vtkSmartPointer::New();
triangulator->SetInputData(segments->GetOutput());
triangulator->Update();
m_Polygon = triangulator->GetOutput();
```
But triangulation isn’t enough to properly display the “hole”. You will probably also have to find all the places where the track intersects itself (where line segments cross), generate a new point at every intersection point, and then cut the intersecting line segments in half:
```plaintext
o o
| |
o-+--o -> o-o--o
| |
o o
```
This would have to be done before the triangulation.
---
### Author:  [@Hedwig\_Huang](https://discourse.vtk.org/u/Hedwig_Huang)
#### Post date: [February 1, 2024, 12:53am UTC](https://discourse.vtk.org/t/delete-the-overlapping-of-the-same-polygon-polydata/13180/4 "2024-02-01T00:53:41Z")
Thanks for your advice!
Later I used `vtkTriangleFilter` and the closed track could be considered as edge and the filter could divide it into bunch of triangles, but the granularity of the triangle seems the reason for the coarse “hole” happening? I tried to recalculate the cross point and update `vtkPoints` but didn’t make it better, so now I try to interpolate more `vtkPoints` or sth else make the polygon curve more smooth, in order to fit smaller triangles to fine the “hole”.
Is it workable?
---
### Author:  [@Hedwig\_Huang](https://discourse.vtk.org/u/Hedwig_Huang)
#### Post date: [February 1, 2024, 7:49am UTC](https://discourse.vtk.org/t/delete-the-overlapping-of-the-same-polygon-polydata/13180/5 "2024-02-01T07:49:48Z")
Good news! I fixed this problem for smoothing curve with the guidance of [https://www.weiy.city/2021/12/vtk-make-interpolation-spline-curve-smoother/](https://www.weiy.city/2021/12/vtk-make-interpolation-spline-curve-smoother/). The curve now looks like this:
But unfortunately, the triangles could not be generated normally, still generating huge triangles…
And now I have a new idea, with the cross point as the dividing line to generate more polygons, with different polygons colored.? Is this ok? But I think this method kinda stupid…