Terminology: Shell or Part?


I was wondering what industry term is usually used when referring to a dinstinct ‘part’ of geometry inside an STL file that is topologically separate from other triangles in the file. Meaning, they share no common edges or vertices between ‘parts’.

I’ve heard some people refer to these as parts, and sometimes as shells (though the latter also seems to get used as a verb describing the process of converting a non-solid mesh with border edges into a closed solid.). Other terms I’ve heard would be “hulls” or “islands”.

Thank you!


I’m not sure if there’s an accepted industry standard term, but I’ve also heard “body” as a descriptor for a topologically distinct region. I’m not a big fan of “shell” – like you said, it has ambiguous association with the shelling operation.

Shell seems like a bad descriptor so I would lean towards islands

My experience with the term “shell” is related to hollowing a volume to a specified wall thickness. A body or volume constitute a fully enclosed or water-tight object, that means there are no openings that, if you were to submerge it in water, would allow water to enter the volume. A part is usually a collection of features that describe a volume’s geometry.