Marius, the issue was clarified by nophead's explanation that "hull() doesn't care about manifoldness". Therefore it is OK that my "obvious" work-around is in fact a work-around and no error is reported. What remains is just a tiny inconsistancy: Logically, a hull-of-a-union should be equivalent to the hull-of-a-union-of-hulls over the same elements. In this specific case is wasn't, because hull-of-a-union triggered a CGAL error while a hull-of-a-union-of-hulls didn't. This confused me. kintel wrote > The CGAL problem is reported - perhaps you were hit by the > error-messages-not-being-cached issue? -- View this message in context: http://forum.openscad.org/hull-issue-or-is-it-me-tp21696p21764.html Sent from the OpenSCAD mailing list archive at Nabble.com.