Maybe "mechanical" was the wrong term, but just brain storming here...
both of these objects have the same splinage, but they don't render to look the same shape. The one on the left looks more like the cross section I modeled, bachelor #2 on the right (with porcelain) is looking fat and puffy.
[attachmentid=18372]
these are both simple, fully enclosed cubes, but porcelain on the right one makes it shade very oddly.
[attachmentid=18373]
BTW this was in V11. Porcelain is slightly different in V13, but i haven't examined it.
here's the prj so you can try it if you dare.
[attachmentid=18374]
porcelainTest.zip