How to only render one vtkRender in vtkRenderWindow with two vtkRenders

[Pisces2018]

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:

I want the result, like this:

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