Nonmanifold headache

# 1 04-04-2010 , 08:53 PM

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Join Date: Jul 2009

Posts: 9

Cheers ladies and gentlemen.

I guess i'm finally forced to post in here, insted of ninja browsing ^^

After some googling and search in here i'm still troubled with nonmanifolds.

I have a character model, nearlly fully modeled in subdiv. and now i want to merge both halfs.
So i attached them under subdiv mode, and went into polygon mode to merge-to-center the vertexs, problem is i'm always getting the error:

// Error: polyToSubdiv1 (Poly To Subdiv Node): One or more edges is nonmanifold.

So, i've done some basic stuff (wich was what i also found on my searches):
- I tried cleaning the mesh with the nonmanifold option toggled, and it seems it doesn't do anything.
- Checked if i didn't have any irregular polygons, they're all fine, only have a few triangulations on the breasts and i don't have any polygon with more then 4 vertexs.

Dunno what else to do, tried converting the subdiv into a polygon and from there i was able to merge everything fine.

But for several stupid reasons, i want to finish the model in sub-div and converting back and foward isn't good for the character heart.

Any tips on what else i can do to will be apreciated.

Cheers,
DJ

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# 2 05-04-2010 , 04:17 AM

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Join Date: Jan 2004

Location: Michigan, USA

Posts: 2,998

The mathematical descriptions of manifold and non-manifold geometry can be quite confusing.

In layman's terms manifold geometry is something that can be manufactured following a specific set of mathematical rules. While, non-manifold geometry refers to geometry that cannot be manufactured following these rules.

An even easier way to put it, is that manifold geometry can be unfolded into a flat polygonal object with all its normals facing in the same direction and all its faces connected by edges, while non-manifold geometry cannot.

There are three types of non-manifold geometry:

(1) T type
(2) Bow_tie type
(3) Flipped_normals type

Here is a short video describing the three types of non-manifold geometry and how to detect and correct them in maya.

https://www.screencast.com/t/MzkzMjA0M

I hope you find this helpful.

Here are the mathematical rules that defines manifold geometry:

-Every interior edge belongs to two faces.
-Every interior vertex is surrounded by one sequence of edges and faces.
-Faces only intersect each other in common edges and vertices
-There is a material on only one side of a face, and the material is on the same side of all faces.

Cheers,
Rick M.

"If I have seen further it is by standing on the shoulders of giants." Sir Isaac Newton, 1675

Last edited by ctbram; 07-04-2010 at 02:45 AM.

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# 3 05-04-2010 , 08:25 AM

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Join Date: Jul 2009

Posts: 9

Cheers ctbram

Thanks for that video, made it clear that most of the texts i found.

Will have a closer look when i get home later.

But now thinkig of this, what might be bugging maya is when i try to connect the first vertex, obviouslly the very first weld will leave 2 faces connected to 1 vertex, but that should be fixed when i weld he 2nd one, but maya keept shouting at me i was doing it wrong.

So perhaps it's becouse of the way i used to connect both subdivs? I used "attach surface" and then went into merging the vertexs (under polygon mode), just wondering if this is something i shouldn't do and it's causing all this.

Thanks anyway user added image

Cheers,
DJ

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# 4 05-04-2010 , 04:06 PM

Lead Modeler - Framestore
Join Date: Feb 2003

Location: UK

Posts: 6,287

Your best bet too is not to do it under the subdiv attach anyway, its a little flaky, it always has been right back to the days of Maya 3. god I feel old!!

Your best bet is to switch back to poly mode, switch on your border edges to see the unattached edges (they are thicker) and then use combine to get the two halves together, followed by merge vertices on a low tolerance so you dont pick up any other verts that dont belong to the ones being merged. Once this is done then convert back to a subd. Also check for flipped normals on the duped half before combining too, just save a lot of hassle later as well.

I used to use subds religiously for years until the advent of smooth poly (keybard 3) its just so much easier to jump back and forth between the low res and a smooth version without the ballache of subd nodes and blind data getting in the way.

best
Jay

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# 5 06-04-2010 , 10:42 AM

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Join Date: Jul 2009

Posts: 9

Well, i really had to go into converting into a polygon to merge both sides.

Probably will stay in it on polygon and move on foward, a bit sad, was really enjoying subdiv, but this is isn't the first issue i've had, and that the only work around solving it was converting the object into polygon mode. Ohh well, time to move foward.

Thanks for the support user added image

Cheers,
DJ

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# 6 06-04-2010 , 03:39 PM

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Join Date: Jan 2004

Location: Michigan, USA

Posts: 2,998

I agree with Jay,

Subd's have a few issues that have been around since all the way back to maya 3.

I tend to use smooth mesh preview (3-key).

One of my gripes with maya subd is that one of its major strengths is to add localized detail and to be able to crease but if you toggle back to polygon for any reason you LOSE all your subd details and have to add them all over again once you go back to subd, which is a waste of time.

"If I have seen further it is by standing on the shoulders of giants." Sir Isaac Newton, 1675

Last edited by ctbram; 07-04-2010 at 02:47 AM.

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# 7 06-04-2010 , 04:03 PM

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Location: New York

Posts: 2,133

I never really got into using sub-ds especially when poly proxy already existed and CPS tools before that. A few setting changes and you could work on the proxy cage side by side with the smoothed mesh and have everything on different layers to avoid bogging down the machine. KB used this method in his Apache tutorial. Now with the smooth mesh preview, you don't even have to do that, though it is still kind of nice as a teaching method when you can see how your splits affect something without toggling back and forth.

"Terminat Bora Diem, Terminal Auctor opus."

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Nonmanifold headache

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