Non manifold geometry maya как исправить

Polygonal geometry can have different configurations or topology types in Maya. Understanding the characteristics of these topologies can be helpful when you need to understand why a modeling operation failed to execute as expected.

Two-manifold topology polygons have a mesh that can be split along its various edges and unfolded so that the mesh lays flat without overlapping pieces.

Non-manifold topology polygons have a configuration that cannot be unfolded into a continuous flat piece. Some tools and actions in Maya cannot work properly with non-manifold geometry. For example, the legacy Boolean algorithm, the Reduce feature, and Sculpting Tools do not work with non-manifold polygon topology. The image below shows three examples of non-manifold topology polygons.

• In the first example (the T shape), more than two faces share an edge. This is known as multiply connected geometry.
• In the second example (the “bowtie” shape), two faces share a single vertex without also sharing an edge.

  This shape is also possible where two three-dimensional shapes share a vertex (such as two cubes meeting at a single point).

• In the third example, a single shape has non-contiguous normals (without border edges). That is, the normal on each polygon face points in an opposite direction. This is a less obvious example of non-manifold geometry.

The following operations in Maya can produce non-manifold geometry:

• Extruding faces or edges with Edit Mesh > Extrude.
• Reversing normals, without extracting geometry (Mesh Display > Reverse).
• Merging vertices, edges or faces into one vertex (Edit Mesh > Merge or Edit Mesh > Merge to Center ).
• Deleting one or more faces.

You can convert non-manifold topology polygons into two-manifold topology (including the less obvious case of adjacent faces with opposite normals) using Mesh > Cleanup.

What is a non-manifold mesh and how to fix it

In your jour­ney through the world of CGI , you have prob­a­bly come across the word non-man­i­fold once or twice. Maybe you got slapped with a “mesh is non-man­i­fold” error too and won­dered how your mesh became non-some­thing. Surely hav­ing a man­i­fold mesh is better.

But what does it mean to be man­i­fold?

A man­i­fold is a math­e­mat­i­cal con­cept relat­ed to space. In a man­i­fold space, objects resem­ble euclid­ean space up close even though they might look dif­fer­ent as a whole. For 3D , this means man­i­fold objects look like a plane when seen up close. Take the earth or any large sphere for instance. It looks plain when you are stand­ing on its sur­face, but the object itself is spherical.

The sec­ond fea­ture of man­i­fold objects is that they are con­tin­u­ous. They wrap with­out any end or begin­ning. Cubes, Spheres, Torus are exam­ples of man­i­fold objects while a plane is an exam­ple of a non-man­i­fold since it’s not con­tin­u­ous. Yep, the good old plane is a non-man­i­fold, who would’ve guessed?

Manifold space can have any num­ber of dimen­sions and it gets weird real fast. But we only care about 3D , so let’s stick to 2‑manifolds. Wait, 2? Remember we use 2D poly­gons to build 3D shapes, there­fore mesh­es are 2‑manifolds.

These con­cepts don’t apply only to com­put­er graph­ics. Our entire uni­verse and every object we will ever hold are 2‑manifolds. Life being 2‑manifold is what allowed tech­niques like UV unwrap­ping to work for CGI . Since we are build­ing 3D shapes from 2D shapes, we can cut them and unfold them into planes in 2D space.

Disclaimer: I’m not a math guy, so I’ve tried to avoid lin­go and keep it focused on 3D . If you are inter­est­ed in the hard­core stuff, check out the Wikipedia page for man­i­fold.

Non-manifolds ruin the fun

Non-man­i­folds com­pli­cate things. For one, they can’t be unwrapped with­out split­ting the mesh. Having islands in the UV Map for con­tin­u­ous geom­e­try is a recipe for a headache.

Boolean oper­a­tions can give you trou­ble too. This has improved by leaps and bounds with Blender 2.80, so it’s not much of a prob­lem any­more. Other soft­ware and algo­rithms may not take non-man­i­folds so kind­ly, though.

On the oth­er hand, Manifold mesh­es are an absolute require­ment for flu­id sim­u­la­tions. They need mesh­es that have a clear sep­a­ra­tion between inside and out­side, which Non-man­i­folds can’t give. Without a con­tin­u­ous sur­face, a mesh can’t encom­pass a closed vol­ume and have an inside.

The biggest issue, and prob­a­bly why you are read­ing this, is 3D print­ing. Remember how our uni­verse is 2‑manifold? Non-man­i­fold geom­e­try can’t exist in real­i­ty. We can’t print float­ing ver­tices or walls with no thick­ness. Even the thinnest piece of paper has some thick­ness. Thickness is also need­ed to have vol­ume, every object we print must have an inter­nal vol­ume. Even “open” objects.

That does­n’t mean non-man­i­folds are always ter­ri­ble, but if you are mod­el­ing for some­thing oth­er than ren­der­ing you will want to fix them.

But I still don’t know what a non-manifold mesh is!

Non-man­i­fold mesh­es aren’t always obvi­ous, but it’s often easy to see that some­thing about the geom­e­try is wrong. The most com­mon prob­lem is an edge con­nect­ed to more or less than two faces.

This also includes inter­nal faces, since one of their edges has to be con­nect­ed to three faces. Edges con­nect­ed to only one face are called Boundary edges and they are also a non-man­i­fold ele­ment. For instance, a plane is a non-man­i­fold with four bound­ary edges.

Separate regions con­nect­ed through a sin­gle ver­tex is what it’s called a bowtie. By regions, I mean mul­ti­ple faces and edges, though two faces alone shar­ing a sin­gle ver­tex can also form a bowtie.

Loose geom­e­try is also non-man­i­fold since it’s not con­tin­u­ous and often does­n’t form a surface.

The most obscure prob­lem is nor­mals point­ing in oppo­site direc­tions for adja­cent faces. This breaks the con­tigu­ous rule since one face is sud­den­ly point­ing the oth­er way as if the sur­face was being twisted.

Please tell me there’s an automatic fix

Nope. To fix a non-man­i­fold mesh you will have to get your hands dirty. But don’t wor­ry, Blender has your back.

Want to get start­ed right away? Use the select menu in the 3D view. Jump into edit mode and make sure all geom­e­try is des­e­lect­ed first, then go Select > All by Trait > Non-manifold Geometry . You can also select more spe­cif­ic prob­lems with loose geometry and interior faces .

Now that you know where the trou­ble is, you can use Blender’s mod­el­ing tools to per­form surgery on the mesh. You can delete ( x ) or sep­a­rate ( p ) loose geom­e­try, fix nor­mals ( Ctrl+N ) or merge ver­tices ( Alt+M ). Don’t for­get about Merge By Distance, which can auto-merge ver­tices that are too close. We used to call this Remove Doubles in pre­vi­ous versions.

Interior faces can be delet­ed right away. Faces con­nect­ed to more than three edges and bound­ary edges may take more con­sid­er­a­tion. A quick way to fix bound­aries is to apply a solid­i­fy mod­i­fi­er or extrude inwards to cre­ate a volume.

I also rec­om­mend installing the Mesh Lint addon. Mesh lint lives in the mesh tab of the prop­er­ties edi­tor high­light­ing all kinds of prob­lems. It even updates in real­time while you work! With this addon by your side, you can fix all non-man­i­folds and be sure you are not acci­den­tal­ly caus­ing oth­er issues like +6 poles.

As you can see, fix­ing a non-man­i­fold mesh is easy once you know what is mak­ing it non-man­i­fold. I hope you found this use­ful and are ready to tack­le non-manifolds!

Creating terrains just got a lot easier.

Mirage lets you cre­ate ter­rains and pop­u­late them with a sim­ple UI and pow­er­ful fea­tures in realtime.

Start cre­at­ing your world today!

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Maya Unfold/Optimize not working

Hi all, have got a very niche issue so not sure if anyone will be able to help, but would be great if anyone can pitch in. Whenever trying to use the Unfold/Optimize features of the Maya UV editor on a mesh I am now constantly getting a «// Error: Unfold3D process error» message. The features do work when unwrapping on simple objects like a cube, sphere, etc. but on more complex geometry it seems to get errors.

Have been trawling the net and pretty sure its based on the fact that I have a Ryzen 3900x CPU installed, causing conflict (another thread with the same issue: https://forums.autodesk.com/t5/maya-forum/unfold3d-process-error/td-p/8679506 ) Also works absolutely fine on my work PC, just not at home. I should add I’ve also updated the PC’s BIOS and downloaded the latest chipset drivers, but still same issue.

Has anyone had similar problems to this/found a work around? Any info would be greatly appreciated. Thanks!

@throttlekitty — Not every time, just on certain meshes that have more complexity than say the primitives, cubes, spheres etc. It could also be to do with non-manifold geometry, but have run clean up and didn’t seem to find any errors. When I extract polys from a mesh, say separate a hand from the body, the piece then unfolds fine — just not when they are one single contiguous mesh.

@oglu — Can confirm still happens on 2020.1.

Spilt the mesh in half and try to unfold both pieces. If one fails split that in half unfold those pieces and so on.

@sprunghunt Have done so, seemed to work after splitting off the hands for example. Only issue is how to find bad geo — I have ran cleanup with all settings and still doesn’t show any bad/non-manifold geometry.

Edit: The weird thing is, Unfold along U and V works great, just not the actual Unfold function Would be nice to be able to use Optimize as well, but for now just using the legacy version.

Many users on systems with newer, high-end CPUs like Ryzen 3900x series have reported issues and ‘Unfold3D Process Error’ messages when unwrapping or optimizing UVs. If you run Maya using one of these high performance CPUs, you can now set the environment variable MAYA_USE_ALTERNATE_UNFOLD_SHIM = 1 to use the Unfold3D tools. MAYA-103288

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Discussion Forum

Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.

Meshing Error

Posted 17 июл. 2012 г., 23:01 UTC MEMS & Nanotechnology, MEMS & Piezoelectric Devices, Geometry, Mesh 6 Replies

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I am new to COMSOL and am trying to model an electrostatically actuated cantilever where the beam is thicker near the tip than at the anchor. When I try to build the swept mesh, I get an error that says «Unsupported topology of domain: domain must be bounded by one connected face component only». What does this error mean? What is the best way to get around it?

I attached my model file where block 1 and 2 form the beam, block 3 is a grounded terminal, and block 4 is the surrounding air.

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first of all you can always use the default mesh that will work.
For sweep mesh you have some limitations, you cannot sweep over topology changes, what you can do is

1) remove or disable the specific union 1 node in your geometry sequence, then
2) to mesh the internal bloc side i.e. boundaries 25 26 27 (once the union has been removed) with tri or quad and then sweep your domains 2, 3, 4 ,5

Then you need to «convert» all external meshed boundaries of your blocks 2,3,4,5 to tri with a «convert» and add a final Free thet mesh for domain 1

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Thanks Ivar. I removed the union and switched to the default mesh (I used the physics defined mesh option).

I next wanted to sweep the voltage on the beam from 1 to 5V and added that to the study. When I ran the simulation, I got the following error:

Failed to find a solution for the initial parameter.
In segregated group 3:
Very ill-conditioned preconditioner.
The relative residual is more than 1000 times larger than the relative tolerance.
Returned solution is not converged.

I’m not quite sure what this means or where to go from here.

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1st you should patch your v4.3, check on the main website
You must check your model, several nodes are not defined, or do not have logical (in my sense) settings. This could come from the fact that when you removed the union, it changed the topology, therefore you must recheck your entity definitions. This is particularly important if you have not defined Selection sets from your different domain and BC lists

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I am simulating a electromechanics model with a beam covered by an air domain. I want to define the mesh by myself and I meet the same problem as presented one in this post.

I follow your steps :

1. add Convert node in Mesh, chose all boundaries of domain 2, 3, 4 ,5
2. add Free Triangular node, build it with «Remain» option.

first of all you can always use the default mesh that will work.
For sweep mesh you have some limitations, you cannot sweep over topology changes, what you can do is

1) remove or disable the specific union 1 node in your geometry sequence, then
2) to mesh the internal bloc side i.e. boundaries 25 26 27 (once the union has been removed) with tri or quad and then sweep your domains 2, 3, 4 ,5

Then you need to «convert» all external meshed boundaries of your blocks 2,3,4,5 to tri with a «convert» and add a final Free thet mesh for domain 1

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if you want to Sweep mesh through a set of domains, you need to add internal boundaries to make the geometry look like a cubic drawing. In your case it’s rather simple, on Block4 add two Layers (only to the LEFT) of respectively 8 and then 12 um, this cut the last block in plane with the internal items. In this way you can mesh the full cut surface (chose at 8 um from the left inside the block, and then sweep out

That should make the trick.
With sweep mesh the initial surface you have meshed need to be swept WITHOUT change all through the domain.
I’m using triangular mesh, it’s simpler and faster, if you want Quads you must work a bit more in manually defining the distributions along the edges

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