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).
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)
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.