# What does this error mean?

**URL:** https://discourse.vtk.org/t/what-does-this-error-mean/1509
**Category:** Development
**Created:** [August 7, 2019, 6:30pm UTC](https://discourse.vtk.org/t/what-does-this-error-mean/1509 "2019-08-07T18:30:36Z")
**Posts on this page:** 2
**Page:** 1

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### Author: ![at123](https://discourse.vtk.org/user_avatar/discourse.vtk.org/at123/32/748_2.png) [@at123](https://discourse.vtk.org/u/at123)
#### Post date: [August 7, 2019, 6:30pm UTC](https://discourse.vtk.org/t/what-does-this-error-mean/1509/1 "2019-08-07T18:30:36Z")

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HI,

I pass a vtkBooleanOperationPolyDataFilter to vtkDelaunay3D. I create a mapper and actor to display it. The actor renders successfully, but I get this error:

vtkDelaunay3D (0x3280c00): 1 degenerate triangles encountered, mesh quality suspect

What does it mean and is there any way for me to fix it?

Thanks. Any help would be greatly appreciated.

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<div class="post-metadata">

### Author: ![Haocheng\_Liu](https://discourse.vtk.org/user_avatar/discourse.vtk.org/haocheng_liu/32/258_2.png) [@Haocheng\_Liu](https://discourse.vtk.org/u/Haocheng_Liu)
#### Post date: [August 7, 2019, 6:34pm UTC](https://discourse.vtk.org/t/what-does-this-error-mean/1509/2 "2019-08-07T18:34:21Z")

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After doing a grep in vtk code base, the error comes from [vtkDelaunay3D.cxx#L516](https://gitlab.kitware.com/vtk/vtk/blob/master/Filters/Core/vtkDelaunay3D.cxx#L516). My suggestion is to understand what’s going on in this filter, if needed, use gdb to go through code step by step and figure out why there are degenerate triangles.