# ​Where is “Relax Polygons” in the latest Slicer version? Any alternatives?

**URL:** <https://discourse.slicer.org/t/where-is-relax-polygons-in-the-latest-slicer-version-any-alternatives/44525>\
**Category:** Support\
**Created:** [September 18, 2025, 5:50pm UTC](https://discourse.slicer.org/t/where-is-relax-polygons-in-the-latest-slicer-version-any-alternatives/44525 "2025-09-18T17:50:20Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![DDD](https://avatars.discourse-cdn.com/v4/letter/d/9fc348/32.png) [@DDD](https://discourse.slicer.org/u/DDD)\
**Post date:** [September 18, 2025, 5:50pm UTC](https://discourse.slicer.org/t/where-is-relax-polygons-in-the-latest-slicer-version-any-alternatives/44525/1 "2025-09-18T17:50:20Z")

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​Hi everyone,

I’m using the latest version of 3D Slicer (version 5.6.2), and I can’t seem to find the “Relax Polygons” option in the “Surface Toolbox” module anymore.

In previous versions, I used “Relax Polygons” regularly to smooth mesh surfaces (such as STL models) before computing curvature using `vtkCurvatures`. This helped reduce curvature calculation errors caused by rough or noisy geometry.

However, in the latest version, Surface Toolbox is still available, but the “Relax Polygons” feature seems to be missing.

Questions:

1.Was “Relax Polygons” removed or renamed in recent versions?

2. Is there another module that includes this functionality?

3. If it’s no longer available in the Graphical User Interface, is there an equivalent method—such as a Python script or another module—to perform the same Laplacian smoothing?

Any advice or workarounds would be greatly appreciated. I rely on this feature for preparing surface models for curvature and morphometric analysis.

Thanks a lot!

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**Author:** ![mau\_igna\_06](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/mau_igna_06/32/9056_2.png) [@mau\_igna\_06](https://discourse.slicer.org/u/mau_igna_06)\
**Post date:** [September 18, 2025, 8:19pm UTC](https://discourse.slicer.org/t/where-is-relax-polygons-in-the-latest-slicer-version-any-alternatives/44525/2 "2025-09-18T20:19:09Z")

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> 1.Was “Relax Polygons” removed or renamed in recent versions?

Hi, yes. Here is the code:

> <https://github.com/Slicer/SlicerSurfaceToolbox/blob/1525a5b5ef0c20566b5888f1b2f8c953c8adc524/relaxPolygons/relaxPolygons.cxx>

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**Author:** ![jamesobutler](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/jamesobutler/32/7511_2.png) [@jamesobutler](https://discourse.slicer.org/u/jamesobutler)\
**Post date:** [September 18, 2025, 8:42pm UTC](https://discourse.slicer.org/t/where-is-relax-polygons-in-the-latest-slicer-version-any-alternatives/44525/3 "2025-09-18T20:42:57Z")

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> [@DDD](#):
>
> 1.Was “Relax Polygons” removed or renamed in recent versions?

It appears to have been removed through the following PR by @lassoan , where he mentions:

> removed relax option (it was the same as smoothing).

> <https://github.com/Slicer/SlicerSurfaceToolbox/pull/41>
>
> This commit replaces 130 files with about 50 lines of code.
> 
> VTK is easily ava…ilable in Python and it is simpler, more flexible, and more portable to run a Python script instead of compiling a C++ CLI module.
> 
> Also fixed extraction of feature edges; and removed relax option (it was the same as smoothing).

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<div class="post-metadata">

**Author:** ![DDD](https://avatars.discourse-cdn.com/v4/letter/d/9fc348/32.png) [@DDD](https://discourse.slicer.org/u/DDD)\
**Post date:** [September 19, 2025, 3:07pm UTC](https://discourse.slicer.org/t/where-is-relax-polygons-in-the-latest-slicer-version-any-alternatives/44525/4 "2025-09-19T15:07:39Z")

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Thanks for sharing the code! I tried to use it but I’m not sure how to make it work in Slicer. Could you please provide some guidance?

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<div class="post-metadata">

**Author:** ![DDD](https://avatars.discourse-cdn.com/v4/letter/d/9fc348/32.png) [@DDD](https://discourse.slicer.org/u/DDD)\
**Post date:** [September 19, 2025, 3:12pm UTC](https://discourse.slicer.org/t/where-is-relax-polygons-in-the-latest-slicer-version-any-alternatives/44525/5 "2025-09-19T15:12:57Z")

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Thanks for sharing the code! I see this is a C++ implementation. Could you guide me on how to implement this in Slicer? Should I compile it as a standalone module, or is there a way to achieve the same smoothing effect using Python and VTK within Slicer’s environment?

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**Author:** ![pieper](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/pieper/32/8_2.png) [@pieper](https://discourse.slicer.org/u/pieper)\
**Post date:** [September 19, 2025, 3:45pm UTC](https://discourse.slicer.org/t/where-is-relax-polygons-in-the-latest-slicer-version-any-alternatives/44525/6 "2025-09-19T15:45:56Z")

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The C++ code looks like just some parameter settings on `vtkWindowedSincPolyDataFilter` so it should be basically trivial to make a python version. If it does something better than what you can do with the smoothing option, you can look at what parameters matter and maybe just expose them in the smoothing option UI.