# The triangle orientation of Constrain vtkDelaunay2D

**URL:** https://discourse.vtk.org/t/the-triangle-orientation-of-constrain-vtkdelaunay2d/2023
**Category:** Support
**Created:** [November 2, 2019, 4:14am UTC](https://discourse.vtk.org/t/the-triangle-orientation-of-constrain-vtkdelaunay2d/2023 "2019-11-02T04:14:46Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![tdchen](https://discourse.vtk.org/letter_avatar_proxy/v4/letter/t/858c86/32.png) [@tdchen](https://discourse.vtk.org/u/tdchen)
#### Post date: [November 2, 2019, 4:14am UTC](https://discourse.vtk.org/t/the-triangle-orientation-of-constrain-vtkdelaunay2d/2023/1 "2019-11-02T04:14:46Z")

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Hi vtkers.  
I made a polygon triangulation with Constrain vtkDelaunay2D.  
But I found the orientation of resulting triangles were not the same.  
The boundary triangles have orientations that consistent with boundary edges.  
But the triangles inside do not.  
Any mistakes I have made with vtkDelaunay2D?  
Or how I can sort the resulting triangles?  
Thank you.