# Solid body vs. sheet body

**URL:** <https://discourse.slicer.org/t/solid-body-vs-sheet-body/34982>\
**Category:** Support\
**Created:** [March 19, 2024, 5:07pm UTC](https://discourse.slicer.org/t/solid-body-vs-sheet-body/34982 "2024-03-19T17:07:18Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Marthe](https://avatars.discourse-cdn.com/v4/letter/m/ba8739/32.png) [@Marthe](https://discourse.slicer.org/u/Marthe)\
**Post date:** [March 19, 2024, 5:07pm UTC](https://discourse.slicer.org/t/solid-body-vs-sheet-body/34982/1 "2024-03-19T17:07:19Z")

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When I export an STL file of the ribcage I segmented from 3D Slicer CTACardio CT scan, I obtain a solid body in CAD software for further processing of the body. However, when I export an STL file of this ribcage after performing an ROI cut, I obtain a sheet body in CAD software. Is there a reason why no solid body is obtained after performing an ROI cut? Is there a solution for this?

Thank you in advance!

Kind regards

a motivated student and admirer of 3D slicer

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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:** [March 19, 2024, 5:33pm UTC](https://discourse.slicer.org/t/solid-body-vs-sheet-body/34982/2 "2024-03-19T17:33:35Z")

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Normal meshes are 3D surfaces, like the one you obtain with Dynamic Modeler ROI cut tool. If you want a tetrahedral mesh you’ll need something like [GitHub - lassoan/SlicerSegmentMesher: Create volumetric mesh from segmentation using Cleaver2 or TetGen](https://github.com/lassoan/SlicerSegmentMesher)

HIH