# Exporting a segment creates a hollow 3D model

**URL:** <https://discourse.slicer.org/t/exporting-a-segment-creates-a-hollow-3d-model/1996>\
**Category:** Support\
**Created:** [January 31, 2018, 10:05pm UTC](https://discourse.slicer.org/t/exporting-a-segment-creates-a-hollow-3d-model/1996 "2018-01-31T22:05:59Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Researcher\_2017](https://avatars.discourse-cdn.com/v4/letter/r/da6949/32.png) [@Researcher\_2017](https://discourse.slicer.org/u/Researcher_2017)\
**Post date:** [January 31, 2018, 10:05pm UTC](https://discourse.slicer.org/t/exporting-a-segment-creates-a-hollow-3d-model/1996/1 "2018-01-31T22:05:59Z")

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Hello,

I am working with the nightly version of 3D Slicer (version 4.9.0). I used the Segment Editor module to create a 3D model of a helmet (shown below).

 ![image1](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/b/f/bf39429e7e3936a1031f157dcdb588ef48d27453.jpeg)

However, when I export the segmentation as a model and save it as a PolyData (.VTK) file, the 3D model is hollow and only shows the outer surface of the segmentation. (shown below)

 ![image2](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/0/6/0676ab1b3010d7b132cba62d543d06f1f7db9b1a.jpeg)

Is there a way that I can produce a model that is completely filled in?

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**Author:** ![lassoan](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/lassoan/32/13_2.png) [@lassoan](https://discourse.slicer.org/u/lassoan)\
**Post date:** [January 31, 2018, 10:56pm UTC](https://discourse.slicer.org/t/exporting-a-segment-creates-a-hollow-3d-model/1996/2 "2018-01-31T22:56:48Z")

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VTK polydata is a polygonal surface mesh: the volume is defined by the enclosing surface. There is no need for elements inside.

What would you like to do with your model? Use it for finite-element analysis? In that case you can use Segment Mesher extension, which creates volumetric mesh (tetrahedral mesh, stored in a VTK unstructured grid) directly from segmentation.

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<div class="post-metadata">

**Author:** ![Researcher\_2017](https://avatars.discourse-cdn.com/v4/letter/r/da6949/32.png) [@Researcher\_2017](https://discourse.slicer.org/u/Researcher_2017)\
**Post date:** [February 1, 2018, 12:31am UTC](https://discourse.slicer.org/t/exporting-a-segment-creates-a-hollow-3d-model/1996/3 "2018-02-01T00:31:56Z")

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Thank you, I’ll try using the Segment Mesher extension. Ultimately, the goal is to print out the complete model on a 3D printer.

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<div class="post-metadata">

**Author:** ![lassoan](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/lassoan/32/13_2.png) [@lassoan](https://discourse.slicer.org/u/lassoan)\
**Post date:** [February 1, 2018, 1:07am UTC](https://discourse.slicer.org/t/exporting-a-segment-creates-a-hollow-3d-model/1996/4 "2018-02-01T01:07:21Z")

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For 3D printing you can only use a hollow model (surface mesh). The printer software will automatically design the fill-in pattern. See tutorial for creating 3D-printable models using Segment Editor: [https://www.slicer.org/wiki/Documentation/Nightly/Training#Slicer4\_Image\_Segmentation](https://www.slicer.org/wiki/Documentation/Nightly/Training#Slicer4_Image_Segmentation)