manifold edges

So I am modeling a hexagonal temple. I created one side and then duplicated it 6 times around the center and ended up with some manifold edges (Ctrl+Alt+M) shows you the manifold edges. You can see them in the attached blend file. I tried to get rid of them by removing doubles.
When I do Ctrl+Alt+M, it selects the manifold edges then if i do remove doubles on those selected vertices, it leaves 12 vertices that are non manifold.
If I select all vertices in the object, it leaves more different manifold edges.

Any idea how to get rid of them? And how I could avoid them by modeling cleaner?


You didn’t attach your .blend file.

Oh thanks! Sheesh…I went to upload it before, but didn’t wait for the upload operation to finish…I must have thought it completed. I believe it’s there now though…thanks.


pagManifoldproblem.blend (804 KB)

you seems to have a lot of divided lines here
are theses necessary ?

i mean you could divide your outside wall and not the inside
that would minimize the vertices count !

you could for instance seperate some of the parts
to minmize vertices qty also!

and instead of 800 probably go down to less 3000

don’t know let us know what your planning to do with this!



You are right. I needed the extra vertices and edges on the outside wall and balcony to create the doors and design on the balcony, but the vertices didn’t need to be on the inner hexagon. However, when I created edge loops, they automatically cut through the inner hexagon as well. If I make the inner hexagon have less vertices, won’t that make the faces triangular? I thought it was good to stay away from triangles.

When you say separate some of the parts, do you mean just have separate objects that are overlapping as if they were one object?

yes to have seperate part would limit the qty of vertices

but also this looks like an hexagone so you could model only 1/6 of it and then apply the spin dup function
what do you think?

start with a circle six sides and model only in 1/6 of the circle then apply the spin dup

shold work i guess


So why is it better to limit the quatity of vertices in an object? Just to make it less complex? Or is there another fundamental reason. I am still learning about 3D modeling, so I just want to be sure why I would change something.

Also, the way I modeled the .blend file I attached was I designed one side of the circle as you say, and then in edit mode did a Shift+D to duplicate the vertices. I then rotated them 60 degrees around the center to create another face of the hexagon. I did this 6 times.
Does the Spin Dup do something a little different? Maybe something that reduces manifold edges?

Is the recommendation to start over, or can these manifold edges be fixed?

Thanks for the discussion!


can you show the 1/6 section or upload the file

usually you try to design with minimum of vertices to limit the size

i eman when you have 100 of objects in a scene that can easily go up to over 1000000 vertices or more so better get use to it and try to minimize when you design
and try if possible to have maximum of quad faces and minimum of tris also
this helps for the render and with normals with UV mapping ect…

it’s only good practice to do so and makes life easier after

the spin dup will automatically reproduce a certain number of time around a circle
but you avhe to calculate before how many in a cetain angle
like 360 / 6 = 60 degrees

this 1/6 is the area wher you design you 1/6 section and it has to fill the side of this triangle or part of a triangle like hexagone

then use dupli vert to multiply 6 times or 5 times to complete the circle and it’s done atuomatically

check out the wiki page for spin dup it wil explain how to sue it - very simple and fast too

now this is valid only if all the section are symetrical all the same



Your non-manifold edges are caused by internal faces. First, remove doubles. Then select all non-manifold. Then press X, Faces to delete faces. If you’re lucky, only your internal faces will be deleted. If you’re unlucky, you may have to do a little rebuilding afterwards.

I’d agree with Ricky - you’re using a lot of vertices. This isn’t necessarily a bad thing, it just makes it more difficult to make changes to your model. You need to try to avoid triangles if you’re going to use subsurf, but your object seems to be quite geometrical and solid, so this might not be a consideration. You could also try using geometry of the type in the attached picture (on the right of your object). It doesn’t have any triangles and won’t create long face loops over your object.


Hey thanks guys…sorry for the delay, wasn’t near my computer this weekend.

I used spin dup, but this still gave me the manifold edges (I believe spin dup is essentially what I was doing before, but instead of pressing a button, I manually was duplicating and rotating 6 times - thanks for the spin dup pointer, saves some time). I then tried what rawpigeon suggested with trying to delete the internal faces, but unfortunately I kept ending up with manifold edges and could not get them to go away.
You guys are absolutely right, I could have approached this better and made my life easier. Rawpiegeon, I like your idea with the little floating ‘door’ indent in your picture, I threw together a quick attempt to do this from scratch, and oddly ended up with some manifold edges when I extruded inward to form a wall. I will have to play around with that.

As for starting over, I believe I will leave my model as is since it doesn’t need any further modifications. I am adding other objects to it to complete it. I will show you guys when I am done, getting close now.
Fortunately the 3D printing service I am sending this to is fixing my manifold edges for me, so I don’t HAVE to get rid of them on my own, but it would be nice to do so.


You had a lot of internal edges, internal faces, overlapping faces and edgeloops that went nowhere. I’ve removed all the non-manifold edges (no guarantees - check the model carefully before using it, etc.). A tip for the future: pay careful attention that you’re only building the outside skin of your objects. The skin should be continuous and consistent. Look out for overlapping faces (they will be darker than single faces) and remember that every face in Blender has either 3 or 4 vertices. If you see anything that looks like a 5 or 6 sided face, it is probably a mistake. Try grabbing the vertices one at a time to see if they are connected to what they should be.


pagManifoldproblem_fixed.blend (704 KB)

Thanks rawpigeon!

When you say in the future to only build the outside skin of an object, should I have done the complete outside of the building and then extruded inwards to get the wall thickness?


There is no one right way to model, but there are things that you should look out for. In your case, it’s internal edges and faces :slight_smile: Just remember to keep checking that you don’t have anything inside your mesh. To take your building as an example, the outside of your wall should only be joined to the inside of your wall at the very top and very bottom. There should not be any faces or edges that jump from the inside wall to the outside - think of these as short-circuits.

If you’re topographically minded, your geometry should be reducible to an n-torus (where n >= 0), i.e. a sphere or a torus with one or more holes. Your building is essentially a torus, a doughnut, with some extra widgets. Unless you’re that inclined to understand things this way, it’s pretty difficult to explain without pictures. It might be easier if I just direct you to the part of the manual that talks about manifold edges so you can avoid them!

I think I get what you are saying, and I certainly see the similarity of a torus and what my shape should be. On my building there were internal faces and edges connecting the outer and inner walls in the middle as well as the top and bottom. I tried to delete these edges and faces, and I kept getting manifold edges elsewhere as well, and couldn’t ever seem to completely rid myself of all the manifold edges.
Thank you for taking the time to explain and fix the building. If you have a link to a tutorial or manual entry on manifold edges, I’d like to have the reference to it.
It’s as you say, I’ll have to be more diligent about checking my mesh more often throughout the design, so I don’t end up with something where it’s hard to pin-point where things starting going wrong.


Here’s a concise bit about what a manifold edge is: