How to fix closed non-manifold poly surface

Good evening everyone,

I’m quite new to rhino…

I’ve been hitting my head against a wall for a few hours now and thought it’s about time to ask the question here. A little info about the project…

Trying to make a 3D printable model of a neighbourhood. Right now I’m preparing a the models of all the buildings (Around a 100-150 buildings). Of course I’m not doing this manually… found a helpful file with most of the buildings done already, the only issue was that it was a .max file. So I converted this to .obj and then imported into rhino.

So here’s the issue I’m currently facing… the result of the import was a bunch of poly and mesh surfaces forming the individual buildings. I firstly deleted all the mesh surfaces so I was only left with the poly surfaces. But when trying to cap each building I realised that most of the buildings have non-manifold surfaces and thus my attempts to cap them are unsuccessful.

Is there any way to reconstruct the surfaces (kind of like shrink rapping them)? Or perhaps a quicker fix?

I also have a .dwg file of the model available. Not sure if that would be a more viable option… I attached an example of one of the buildings with a non-manifold surface. Keep in mind that there are 100+ buildings so manually going in and adjusting the control points does not seem like a viable option for me.

Appreciate the help!
Example.3dm (4.0 MB)

Hi Tim - first, MergeAllCoplanarFaces then (easier in wireframe display) ShowEdges >NonManifold - then ExtractSrf the interior faces where you see the nonmanifolds highlighted.
Hm- there is some other ugly internal stuff in there to clean up as well.

@tim.brammer here it is cleaned up, I think, but if you have more of these to do I would try to find a reliable workflow - ExtractSrf, Delete or Untrim, Trim, Cap are what I used here.

Example_PG.3dm (222.1 KB)


Hi @pascal
Thank you so much for your prompt reply! Going to try that out right now, the example you sent looks perfect… exactly what I need.