Exporting a segment creates a hollow 3D model

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

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

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

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.

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

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