# 180 degree Flip in STL/PLY when imported

**URL:** <https://discourse.slicer.org/t/180-degree-flip-in-stl-ply-when-imported/33447>\
**Category:** Support\
**Tags:** stl, meshing\
**Created:** [December 18, 2023, 8:27pm UTC](https://discourse.slicer.org/t/180-degree-flip-in-stl-ply-when-imported/33447 "2023-12-18T20:27:26Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Vignesh\_Chakravarthy](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/vignesh_chakravarthy/32/66674_2.png) [@Vignesh\_Chakravarthy](https://discourse.slicer.org/u/Vignesh_Chakravarthy)\
**Post date:** [December 18, 2023, 8:27pm UTC](https://discourse.slicer.org/t/180-degree-flip-in-stl-ply-when-imported/33447/1 "2023-12-18T20:27:26Z")

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Hi,  
I am using Slicer 5.2.2. I have saved lesions and prostate from Ultrasound as landmarks in slicer. Then, imported landmarks into MATLAB for non-rigid registration. I converted them to ply/stl from pointcloud after transformation and when I imported them back to slicer it is flipped 180 degree.  
Please let me know how to avoid this angle flip.

 ![STL flip](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/f/3/f3ee22a8887cb986dbe989274618f80a300bc0e5.png)

Regards,  
Vignesh

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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:** [December 18, 2023, 10:30pm UTC](https://discourse.slicer.org/t/180-degree-flip-in-stl-ply-when-imported/33447/2 "2023-12-18T22:30:28Z")

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You can search for LPS / RAS and will get lots of information about how to keep track of the relationship between images and meshes in different programs.

E.g. [Coordinate systems — 3D Slicer documentation](https://slicer.readthedocs.io/en/latest/user_guide/coordinate_systems.html)

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<div class="post-metadata">

**Author:** ![Vignesh\_Chakravarthy](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/vignesh_chakravarthy/32/66674_2.png) [@Vignesh\_Chakravarthy](https://discourse.slicer.org/u/Vignesh_Chakravarthy)\
**Post date:** [December 19, 2023, 6:33pm UTC](https://discourse.slicer.org/t/180-degree-flip-in-stl-ply-when-imported/33447/3 "2023-12-19T18:33:32Z")

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Hi,

I used transform technique in Slicer (Inferior - Superior - 180 deg) to align the imported PLY files with the existing Ultrasound prostate model. Thanks for letting me know about the coordinate systems.

Best,  
Vignesh