UV shells moving position when reopening a file

[Anonymous]

I am often finding that when I open a Maya scene that my packed UV shells will have moved position and ruined their UV layout. This issue only seems to occur on assets that a comprised of multiple separate meshes.

I do a lot of UV mapping for game assets. As part of the baking process I require that assets sometimes be separates into multiple components. The UVs of these separate meshes are laid out / packed together so that the fit within 0 - 1 UV space, as if they were one object.

The issue I am encountering is that after, painstakingly laying out the UVs for these meshes, if I close Maya and come back to work on the asset at later date, sometimes the UV shells for this geometry will have shifted position and ruined the layout.

One of the key reasons why this bug causes such problems is that my assets often utilize a lot of  shared UV space. Any changes to the UVs mean that I need to manually copy and paste the geometry with updated UVs for any place I have shared UV space. This is a HUGE pain.

I don't have a clear way to reproduce this issue but it's gotten so bad that I'm forced to try and complete the UV / baking process all in one session of Maya, just in case all the UV work is lost if I delay the bake process until a later date.

Some things that I often do as part of my workflow that might be relevant to tracking down the bug:

- I often group and un-group the meshes for export (substance painter requires meshes to be outside groups in order to use 'match by mesh name' bake functionality).

- The UV Layout operation is applied to the meshes when they are already separated from one another.

- I might combine the meshes together and then separate them again at a later date (I have not seen this cause issues during the Maya session that this is carried out though).

I am using Maya LT but have also had this issue occur in the Beta version of Maya.

[sean.heasley]

Hi @Anonymous

When you go to use the layout tool, have you tried using legacy?

Also do you use multiple UV sets? There was an issue in the past with a users UVs moving when they would go from Maya 2017 to 2016 and it was due to multiple UV sets so an issue like that may be present here.

If neither of these suggestions work, when you get a chance, can you please zip and attach the scene file here or via dropbox/google drive or another file sharing program so I can take a look at it?

Let me know if anything changes!

[sean.heasley]

Hi @Anonymous

Just wanted to check in to see how things were going. Are you still having this issue?

If your issue is resolved, please click Accept as Solution on the posts that helped you so others in the community can find them easily.

[Anonymous]

Hi @sean.heasley! is this thread still open? I do have a file with this problem so maybe it could help you see. I packed the Uvs cleanly and if you re/open it you can see the they are out of place. The funny thing though is that if the file is just been opened and no other action has been made, you can select all the uv islands, move them, and undo with Ctrl+Z. This line of actions seems to put the UVs back to place. 

Now Obviously this is just a workaround and sometimes, after opening a file I forget to check if the Uvs have shifted and en up having to redo them again so please, fix this.

Also, for some reason this reply is not being posted with the file attached so here it is  for my dropbox download:

https://www.dropbox.com/s/f9luypj65d99dqi/SM_DV_Bed_05.mlt?dl=0

[sean.heasley]

Hi @Anonymous and welcome to the community!

Thanks for attaching the scene file!

I was able to reproduce your issue so as a test I selected the entire bed and used Freeze Transformations and Delete History.

I then saved the scene file and just added _01 to it and re opened the scene and the issue was gone.

When you get a chance can you please try these steps and let me know if they work for you?

If one or more of these posts helped answer your question, please click Accept as Solution on the posts that helped you so others in the community can find them easily.

Kudos are greatly appreciated. Everyone likes a thumbs up!

[Anonymous]

It does work, if I fix the uvs with the Undo method I described above, then save the file, it gets fixed. The thing is that it still happens in other scenes, and after saving and closing my files I always freeze transforms and delete history. Sometimes, when I re/open the file, it is fine, Other times, the Uvs are out of place. As @Anonymous said, It is pretty difficult to replicate this bug. I just happened to have a file that had the bug.

[sean.heasley]

Hi @Anonymous

Yeah it is hard to reproduce.

If you make a new scene file with a basic cube, uv it and save does this still occur or is it only on specific scene files?

You may want to try deleting your settings/preferences.

Let me know if anything changes!

[Anonymous]

Yup, It is on very specific scenes.

I'll try and delete the Settings/Preferences as you said and come back in a while to let you know if that made a diference.

[sean.heasley]

Hi @Anonymous

I'm just checking in again to see if you need more help with this. Did resetting your prefs work?

If so, please click Accept as Solution on the posts that helped you so others in the community can find them easily.

[Anonymous]

Nope still happens. 

Maya just openedAfter the "Move / Undo" trick to correct it

[sean.heasley]

Hi @Anonymous

Hmmm ok.

This is probably related to something going wrong in the scene files. When you get a chance, can you try exporting everything from the scene as an fbx then import it into a new scene file, save and see if the issue still occurs?

[Anonymous]

When exportin, be that as an fbx or obj. the worng UVs will be exported as well.

Now. since this happens at random, I would not be able to know it the next time I open a scene the UVs will be moved so it is hard for me to asses when to save a scene as an fbx. I think I can take some time when working and make two copies: the .mlt and the .fbx  and come back to you later.

[sean.heasley]

Hi @Anonymous

What you should be able to do, is use the CTRL+Z method you mentioned to "fix" the UVs that way they are laid out correctly.

Once they are like that then export everything as an fbx and import it into a new scene. That way the imported objects should have the correct UVs and they should stay that way.

[Anonymous]

Oh yeah. after doing that, the issue is fixed, even in the Maya scene. If you fix it with the Undo  trick, save, and re-open it is fixed. The problem is not that the Uvs that got messed up stay that way forever. If you fix them by hand or with the undo method and save the scene, the issue is gone. The problem is that it happens sometimes and we have now way to know when or how. Now, one thing I have noticed is:

Case 1 - If in a single maya session I model and lay out Uvs, then close the scene and I come back to it (let's say next day) and open it, the UVs are messed up.

Case 2 - If in a session I just manage to model, then save and close maya and the next day I finish the Uvs, then save and close again. When I come back to the model, the Uvs are all right.

Now with session I mean that i never cloesd maya during that work time. Also this is not always true but it is what I have experienced the most

[sean.heasley]

Hi @Anonymous

Right I understand that part.

The reason I'm asking about doing the export is because if you "fix" the UVs then export everything as an fbx and import it into a new scene the UVs should stay fixed even if you save, close and re open Maya.

Since this is only happening with specific scene files it can be tough to troubleshoot like you said but I'm hoping the fbx import/export option will solve this.

[Anonymous]

Yes, the fbx export import fixes that, but just for that one scene; when i work on new scenes the same Uv issue happens

Now for me is not sucha big deal. I have gotten used to checking my UVs when openining a Maya scene. but it feels unnecesary and gets annoying when you have to check various scenes  for this. 

[sean.heasley]

Hi @Anonymous3

Ah I'm sorry I misunderstood, I didn't realize this was happening on new scenes for you as well as the old ones.

Since this is happening with new scenes and not just specific scene files it looks like somethings gone wrong with the core of Maya.

Since resetting your prefs didn't work, you may want to perform a clean uninstall/reinstall of Maya.

This should completely prevent you from seeing this issue again in the future.

[mspeer]

Hi!

@Anonymous

I would be interested to have a look at the file too, if you enable the file-download again.

[Anonymous]

@sean.heasley Ok. I'll reainstall maya when I get my new ssd (about 2 weeks from now) and I'll get back to you again.

@mspeer Sorry but the file has been fixed so it no longer shows the bug so no use to uplaod it again 😕

[sean.heasley]

Hi @Anonymous

While I don't mind waiting for you to have your new SSD, performing a clean uninstall/reinstall shouldn't take too long so if I don't mind if you'd like to try it before then or if you'd rather wait