From: AlexSD (ALEXANDERSD)
Hello guys
Im pretty sure what im make some mistakes on early stage of surfacing, but anyway, now i try to understand where, and why shell operation creating articacts.
Can some give some advice?
Attachments:
chair_umbrella_shell_problem.3dm
Image Attachments:
shell_problem.JPG
shell_problem_overview.JPG
From: Michael Gibson
Hi Alex, the shell function in the geometry library that MoI uses is pretty limited. For thickening an open surface like you have here it is only able to do that if the surface is all smooth at every edge. If it has any areas where the surfaces are not tangent where they meet at an edge, the offset surfaces do not naturally meet up themselves but instead need to be extended and intersected and it is that area that is not handled well by MoI currently.
So for your case here, the problem you show is at a spot where the surfaces are not smooth on either side of the edge:
Things that are kind of close to being smooth but just a little bit off can actually be even more difficult for shelling because 2 surfaces that meet at a shallow angle have more of a meandering "zone of intersection" between them rather than a sharply defined intersection. So it makes things that are going to try and extend and intersect even more difficult.
In cases where shell is not going to be possible you may need to directly model the interior walls.
Another thing that will not shell well is something like this where the surface has been squashed down to a point along one edge:
The surface normal direction becomes poorly defined in the collapsed area and generating an offset surface involves evaluating points that are displaced along the surface normal so if the normal is oscillating wildly it won't make for a good offset surface.
- Michael
Image Attachments:
alex_shell1.jpg
alex_shell2.jpg
alex_shell3.jpg
