# Changes to VTK polydata between 4.10 and 4.11

**URL:** <https://discourse.slicer.org/t/changes-to-vtk-polydata-between-4-10-and-4-11/17348>\
**Category:** Support\
**Tags:** vtk\
**Created:** [April 27, 2021, 12:25pm UTC](https://discourse.slicer.org/t/changes-to-vtk-polydata-between-4-10-and-4-11/17348 "2021-04-27T12:25:51Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![codey](https://avatars.discourse-cdn.com/v4/letter/c/ea666f/32.png) [@codey](https://discourse.slicer.org/u/codey)\
**Post date:** [April 27, 2021, 12:25pm UTC](https://discourse.slicer.org/t/changes-to-vtk-polydata-between-4-10-and-4-11/17348/1 "2021-04-27T12:25:52Z")

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I have noticed that VTK meshes imported in 4.10 and 4.11 differ in their spatial location. Rotation by 180 corrects for this. I presume this is down to a different interpretation of the VTK coordinate system. between the slicer versions. Does anyone know why these are different?

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**Author:** ![Andinet\_Enquobahrie](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/andinet_enquobahrie/32/75_2.png) [@Andinet\_Enquobahrie](https://discourse.slicer.org/u/Andinet_Enquobahrie)\
**Post date:** [April 27, 2021, 1:30pm UTC](https://discourse.slicer.org/t/changes-to-vtk-polydata-between-4-10-and-4-11/17348/2 "2021-04-27T13:30:08Z")

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This is probably due to the change in 4.11 in the way coordinate system of model files are handled in 3D Slicer

> [@Model files are now saved in LPS coordinate system](https://discourse.slicer.org/t/model-files-are-now-saved-in-lps-coordinate-system/10446):
>
> While Slicer uses RAS coordinate system internally, images, transforms, and markups files are stored in LPS coordinate system, because DICOM and all medical image computing software (maybe except a few very old ones) uses LPS coordinate system in files. However, Slicer has been still using its internal RAS coordinate system in mesh files (STL, VTK, VTP, OBJ, PLY), which [caused issues when interfacing with third-party software](https://issues.slicer.org/view.php?id=4445). Starting from tomorrow (Slicer-4.11.0-2020-02-26, revision 28794), …