Avoiding random non-manifold faces/UVs

Lucasthyel

Hey, I'm fairly new to this and trying to UV a character while fixing some problems in the mesh, and at some point, I always end up getting non-manifold UVs, which makes impossible to further unfold the mesh or do a lot of important operations. Any idea on what I'm doing that create this kind of problem? As far as I'm aware of, I'm only moving vertices, using sculpting relax function, merging duplicated vertices, creating/deleting seams and unfolding the mesh. How can I avoid creating random non-manifold faces? And more important, how to fix the model? Cleanup won't do the trick (it destroys everything). In the screenshot below are the faces that Maya marks as non-manifold. It's my third try and I end up destroying the mesh and redoing the UV process from zero when a non-manifold face appears. Thanks!


EDIT: Solved! See BIGTIMEMASTER's reply below for the solution.

Alex_J

I can't say exactly what is causing the issue in the first place, but if you do much mirroring at all that can give you some extra vertices along the border which will cause issues. Projecting your UV's should have anything to do with this.

There are two main ways I ameliorate the issue -- both are a little tedious but it's just a few minutes work really after you've done it a time or two. What I do is turn on vertex selection mode and then turn on smooth mesh preview. This will pull any extra vertices out from hiding and you can pinpoint the problems directly. Also you can use your cleanup operation but set it to only select, save those selected faces as a quick selection, and then just replace the faces one by one.

One more alternate solution if you like a more intuitive approach is to duplicate your mesh, set the first one as live, and turn on quad draw for the second. Now you can go in and just drag-drop weld vertices or quickly delete and refill bad quads.

As a beginner I had this trouble a lot as well. But nowadays I don't face it very much at all. I wish I could say what exactly was causing it.

apollo580

I occasionally get these after re-topology in Topogun. Usually I messed up along the way and the vertex's didn't weld properly or normals were flipped, or even faces sat directly on to top of each other.

Now for the solution...

Maya is total trash for automatic fixing IMO, I've tried multiple settings and it never fixes the mesh for me. I usually go to the "Clean Up Mesh" tab and check for non-manifold geometry and make sure I don't fix it but instead select it. This then highlights the problem areas. Then I try and manually weld the points and see if that's the issue. Other times I delete faces and check if there are any overlapping problems. In general I go back to topogun and fix the mesh there, always seems easier there.

Hope this helps!

Lucasthyel

BIGTIMEMASTER said:

I can't say exactly what is causing the issue in the first place, but if you do much mirroring at all that can give you some extra vertices along the border which will cause issues. Projecting your UV's should have anything to do with this.

There are two main ways I ameliorate the issue -- both are a little tedious but it's just a few minutes work really after you've done it a time or two. What I do is turn on vertex selection mode and then turn on smooth mesh preview. This will pull any extra vertices out from hiding and you can pinpoint the problems directly. Also you can use your cleanup operation but set it to only select, save those selected faces as a quick selection, and then just replace the faces one by one.

One more alternate solution if you like a more intuitive approach is to duplicate your mesh, set the first one as live, and turn on quad draw for the second. Now you can go in and just drag-drop weld vertices or quickly delete and refill bad quads.

As a beginner I had this trouble a lot as well. But nowadays I don't face it very much at all. I wish I could say what exactly was causing it.

I mirrored once in the beginning when finished retopology, but had no non-manifold faces for quite a while until the cleanup stage. tried your suggestion, but unfortunately, the mesh doesn't look different when using smooth mesh preview. And deleting the faces and re-creating them with quad draw also re-creates them as non-manifold faces, not sure why. The mesh itself looks fine, apart for some extra vertices I already cleaned up. I'll try re-doing the cleanup from scratch and carefully see when the first non-manifold face shows up. Thanks for the input!

apollo580 said:

I occasionally get these after re-topology in Topogun. Usually I messed up along the way and the vertex's didn't weld properly or normals were flipped, or even faces sat directly on to top of each other.

Now for the solution...

Maya is total trash for automatic fixing IMO, I've tried multiple settings and it never fixes the mesh for me. I usually go to the "Clean Up Mesh" tab and check for non-manifold geometry and make sure I don't fix it but instead select it. This then highlights the problem areas. Then I try and manually weld the points and see if that's the issue. Other times I delete faces and check if there are any overlapping problems. In general I go back to topogun and fix the mesh there, always seems easier there.

Hope this helps!

I double checked for some weird faces/vertices along the mesh and found some extra vertices really close to each other, but apart from that, nothing that my current knowledge can see right off the bat. Comparing my mesh with this definition of non-manifold geometry, it doesn't look like the faces that Maya marked have any of this problem, so I think the problem is somewhere else. I'll try once again tomorrow to do from scratch and observe when the first non-manifold geometry appears. Thanks for the info!

Alex_J

i'm working in maya right now. if you upload the scene file i can take a look at it.

Lucasthyel

BIGTIMEMASTER said:

i'm working in maya right now. if you upload the scene file i can take a look at it.

Oh, nice, here it is: [solved]

Alex_J

When I run mesh cleanup, this is what I get :

And within each of the problem faces, an extra vertex, as I suspected. All you got to do is delete these vertices. You can also just delete the face and bridge a new one in.

See, all along the seams here. It always happens during mirror operations. I dunno if it's a bug or what, but usually after doing a mirror I do a quick cleanup and delete these extra vertices out.

Lucasthyel

BIGTIMEMASTER said:

When I run mesh cleanup, this is what I get :

And within each of the problem faces, an extra vertex, as I suspected. All you got to do is delete these vertices. You can also just delete the face and bridge a new one in.

See, all along the seams here. It always happens during mirror operations. I dunno if it's a bug or what, but usually after doing a mirror I do a quick cleanup and delete these extra vertices out.

Yeah, I noticed some of them while cleaning but totally missed other ones, thanks for the help! Weird thing is that I only use mirror in the beginning of the process, and after doing a planar mapping, I could unfold without problem. I must've put these extra vertices somehow later while doing stuff, just can't remember what tool can do that since I'm not really adding extra geometry at this stage.

EDIT: Are these faces the only ones that are non-manifold on your side? Mine shows tons even around the ear, feet etc.

Alex_J

yeah those faces you can see in the wireframe is everything mesh cleanup found. I'm using the latest version of Maya 2018.

UV mapping shouldn't have anything to do with these faces or extra vertices. This looks like the type of thing that happens when I do a mirror operation. I can't think of any other instances in which this sort of thing happens. But anyway, once you know how to find them and clean them up it's no big deal.

For the eyes, to check them, you need to grab the vertices on the selected faces and wiggle them with the move tool. You wil l find that some are unwelded. Smooth mesh preview will show this as well (in the file you sent me they all seemed to be welded, I am just saying if they are coming up as non-manifold). If the vertices are riding on top of each other you can fix it easy be doing mesh>merge and setting a value of 0.1. This will weld only vertices that are right on top of each other.

Not sure what would cause your eyes to have unwelded verts, but as you develop more experience you'll encounter stuff like this less or at least be able to clean it up quickly.

Lucasthyel

BIGTIMEMASTER said:

yeah those faces you can see in the wireframe is everything mesh cleanup found. I'm using the latest version of Maya 2018.

UV mapping shouldn't have anything to do with these faces or extra vertices. This looks like the type of thing that happens when I do a mirror operation. I can't think of any other instances in which this sort of thing happens. But anyway, once you know how to find them and clean them up it's no big deal.

For the eyes, to check them, you need to grab the vertices on the selected faces and wiggle them with the move tool. You wil l find that some are unwelded. Smooth mesh preview will show this as well. If the vertices are riding on top of eachother you can fix it easy be doing mesh>merge and setting a value of 0.1. This will weld only vertices that are right on top of each other.

Not sure what would cause your eyes to have unwelded verts, but as you develop more experience you'll encounter stuff like this less or at least be able to clean it up quickly.

Great! I'm able to unfold and continue the model. I think I will do just fine about this problem in future models now, thanks for the explanation!