# how to make rounded trapezoid vtkPolyData or vtkPoints

**URL:** https://discourse.vtk.org/t/how-to-make-rounded-trapezoid-vtkpolydata-or-vtkpoints/8780
**Category:** Support
**Created:** [June 22, 2022, 7:54am UTC](https://discourse.vtk.org/t/how-to-make-rounded-trapezoid-vtkpolydata-or-vtkpoints/8780 "2022-06-22T07:54:14Z")
**Posts on this page:** 3
**Page:** 1

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### Author: ![hye00525](https://discourse.vtk.org/user_avatar/discourse.vtk.org/hye00525/32/4904_2.png) [@hye00525](https://discourse.vtk.org/u/hye00525)
#### Post date: [June 22, 2022, 7:54am UTC](https://discourse.vtk.org/t/how-to-make-rounded-trapezoid-vtkpolydata-or-vtkpoints/8780/1 "2022-06-22T07:54:14Z")

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hello, i’m trying to get vtkPoints (or vtkPolyData) that make up the rounded trapzoid shape.  
like below,

 ![image](https://discourse.vtk.org/uploads/default/original/2X/2/28f1a838281c75f83cc9cbcf177565ce047dad14.png)

I would like to set the diameter of the rolling circle as a parameter as below.  
 ![image](https://discourse.vtk.org/uploads/default/original/2X/3/314083a3ba37766c74b3d5bef68a7534ae03eb4a.png)

is there good idea? or code example for this?  
thank you

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### Author: ![Paulo\_Carvalho](https://discourse.vtk.org/user_avatar/discourse.vtk.org/paulo_carvalho/32/370_2.png) [@Paulo\_Carvalho](https://discourse.vtk.org/u/Paulo_Carvalho)
#### Post date: [June 25, 2022, 9:27pm UTC](https://discourse.vtk.org/t/how-to-make-rounded-trapezoid-vtkpolydata-or-vtkpoints/8780/2 "2022-06-25T21:27:05Z")

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Hi,

I don’t know any VTK classes that can do that in a single shot. Most likely you’ll need to use a `vtkPath` class ([https://vtk.org/doc/nightly/html/classvtkPath.html](https://vtk.org/doc/nightly/html/classvtkPath.html)) to define a sequence of instructions to lay out a series of connected straight lines and Bezier curves in order to compose the desired shape.

take care,

Paulo

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### Author: ![mau\_igna\_06](https://discourse.vtk.org/user_avatar/discourse.vtk.org/mau_igna_06/32/8064_2.png) [@mau\_igna\_06](https://discourse.vtk.org/u/mau_igna_06)
#### Post date: [June 25, 2022, 10:59pm UTC](https://discourse.vtk.org/t/how-to-make-rounded-trapezoid-vtkpolydata-or-vtkpoints/8780/3 "2022-06-25T22:59:00Z")

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I think you may have to create 2 types of different functions: one for linear segments, one for circular arcs