# How to only render one vtkRender in vtkRenderWindow with two vtkRenders

**URL:** https://discourse.vtk.org/t/how-to-only-render-one-vtkrender-in-vtkrenderwindow-with-two-vtkrenders/11425
**Category:** Development
**Tags:** code
**Created:** [May 10, 2023, 11:48am UTC](https://discourse.vtk.org/t/how-to-only-render-one-vtkrender-in-vtkrenderwindow-with-two-vtkrenders/11425 "2023-05-10T11:48:31Z")
**Posts on this page:** 1
**Showing post:** 8

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### Author: ![Pisces2018](https://discourse.vtk.org/user_avatar/discourse.vtk.org/pisces2018/32/7063_2.png) [@Pisces2018](https://discourse.vtk.org/u/Pisces2018)
#### Post date: [May 11, 2023, 3:33am UTC](https://discourse.vtk.org/t/how-to-only-render-one-vtkrender-in-vtkrenderwindow-with-two-vtkrenders/11425/8 "2023-05-11T03:33:14Z")

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Thanks for your kindly reply!  
At first, I hope the polygon is filled, but during the drawing process, the problem of concave polygons and self-intersecting polygons can occur, which can lead to repeated drawing.Like this:

 ![876231236186160](https://discourse.vtk.org/uploads/default/original/2X/2/2e7ca7532d2c9dc0156a5673f4693c710cb5a393.png)  
I want the result, like this:  
 ![WeChat Screenshot_20230416155916](https://discourse.vtk.org/uploads/default/original/2X/7/7d96f9d0a6f9506c24ce26403e2c8f21dbb3c5d7.png)

Because this problem is not solved, I now want the polygon to be empty!

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