do mean to add some empty space between the segments by shrinking the margin of the segments?
would you please let me know in which step I should avoid smoothing?
I need to create a volumetric mesh for these geometries, therefore, I have to work with the meshes and I have no idea how can I use the labelmap to create the volumetric mesh.
I thought that setting the smoothing factor to the zero only effects the 3D visualization and does not affect the exported geometries from the Slicer. Please correct me if I am wrong.
You can use Segment Mesher extension to create volumetric mesh directly from segments. Cleaver method generates mesh from the labelmap representation (not from surface mesh) and creates a joint, multi-material tetrahedral mesh, with guaranteed no overlap or gap between materials (segments).