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Most of my work with Blender involves modifying stl files of models of fingers, hands and forearms. Sometimes Boolean operations suffice and leave a manifold mesh. However, when a small portion of the file needs to be modified and added to another file, I'm still faced with too many instances of working with vertices and edges and not getting great results. The name "skin" suggests that a surface would be formed over some existing objects and create a manifold. However, the manual's description of working with vertices and the examples seem to indicate that "skin" isn't really suitable for fixing non-manifold objects. Adventures with shrinkwrap don't yield desired results. Consider this pivot/hinge. I want to extend it with a rectangular box. Sizing the box so that it just fits over the pivot part above the hole results in a mesh which would appear to be easy to automatically make it manifold.
I couldn't figure out how to do it. Have I overlooked something in skin/shrinkwrap or is there another route or add-on which I need to explore? TIA. LeftHinge

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I think a good starting point may be this:

enter image description here

I used Limited Dissolve mode from X menu. It effectively gets rid of mess edges and faces of the mesh.

Then I used some very basic tweaking like dissolving some edges and vertices to make them not repeat each other, and creating some new edges instead of old ones. I also recalculated normals (Ctrl+N) and made them point outside.

enter image description here

Finally, I added Shrinkwrap modifier, imported original mesh again and wrapped my result atop of it so to be sure (hope so) that the form of the original mesh was preserved (the original mesh is hidden on the screenshot).

blend file here

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  • $\begingroup$ Your image is the result of shrinkwrapping the cleaned part? When I tried shrinkwrapping, the hole was covered. Do you think that was from the messy mesh or did I miss some setting? $\endgroup$ – Hertfordkc Aug 4 '15 at 11:28
  • $\begingroup$ No, the original mesh is hidden on screenshot (and thus shrinkwrapping too). If revealed, it looks like this. LeftHinge is the cleaned mesh, LeftHinge.001 is the original mesh. Shrinkwrap is with default settings (it corrects not so much, but let it be). I'm not sure why Shrinkwrap covered the hole for you (probably you haven't corrected everything needed). You may want to look into the .blend for more details. $\endgroup$ – Mr Zak Aug 4 '15 at 16:59
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I think you won't get good geometry with shrinkwrap. Also the skin modifier works completely different (see https://www.blender.org/manual/modifiers/generate/skin.html). You rather would use shrinkwrap to put labels onto surfaces and similiar things.

I opend your stl file and it is really a mess geometry wise. Can you tell how this was created?

I think the best would be to rebuild the mesh.

Edit: Maybe my answer was a bit misleading or even wrong regarding the usage of the shrinkwrap modifier. If you would do a retopology of your mesh you would use the shrinkwrap modifier for the workflow (see tutorials on youtube).

I'm not sure what you want to archieve. I made a .blend with a working (?) shrinkwrap on your mesh.

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  • $\begingroup$ Thank you for confirming that neither skin or shrinkwrap has options to do the job. I don't know how the original stl file was created. I expect that the project would be much easier if I had the original design file and software. $\endgroup$ – Hertfordkc Aug 3 '15 at 12:12
  • $\begingroup$ Any opinion on the 2nd part of my question: conceptually, if a sleeve if generally fitted onto a mangled part, shouldn't it be possible to create a "skin" based on "outside" vertices of the two parts? The "skin" would thus be manifold. $\endgroup$ – Hertfordkc Aug 3 '15 at 12:17
  • $\begingroup$ after re-topoing, you can use a shrinkwrap just to make sure your new model lines up nicely with the old. $\endgroup$ – Scalia Aug 3 '15 at 14:49

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