Maya crashes upon exporting to .dae after UV editing and/or change of texture

Lutricia Roux · January 28, 2013

Hello, I have a bit of odd problem I've been trying to solve without any luck and thought I give it a last try to solve it by asking here for advice before I start over from scratch.

I'm working in an old Maya (2008) but have so far managed to both rig, export, upload etc mesh and successfully import to SL. This last job is giving me a bit of a headache though. I'll try to describe it in detail in case someone perhaps might be able to point out where I go wrong.

First thing was that I forgot to set the UV maps before I did the actual rigging. I exported the model, uploaded and realized I forgot the UV mapping. Fair enough, I thought. I export the skin weight maps, fix the UVs, import them back and try again. Export worked good, uploaded to SL and mesh looked ok.

Q1: This step puzzles me, should this really be possible, isn't the skin weights reliant to the UVs and the actual rig would be destroyed now by me editing the UVs after the actual weight painting?

Again, I forgot to set different textures for each face. Back again, apply textures to selected faces and now the problem starts. Everytime I try to export the mesh, either unrigged or rigged, Maya crashes. Other parts in the scene works, but not the actual body of the character (i.e rigged clothes etc export without any problem).

The model is not extremelly detailed, not high count on anything, which I thought was the issue first, because previously I had to export the scene in parts for Maya not to crash.

Q2: Do anyone have an idea of what it is that makes Maya crash on export like this? I never experienced similar.

Q3: Suggestions of things to try to enable to export, is it my computer lacking enough memory, can I alter some settings in Maya etc?

Note, I have even tried to import the mesh into a new scene, new skeleton, rig it and ... crash. Always after I apply textures. I tried to apply both the standard Maya textures (checkered) as well as own created ones. No luck.

I also (since I think as I ask in Q1, that it does affect it) detached the mesh from the skeleton, deleted all history, attached again so it shouldn't be affected by my previous mistake. No luck.

I know it is a lenghty post, please ask if I need to clarify some steps, thank you!

Chosen Few · January 29, 2013

Lutricia Roux wrote:

I export the skin weight maps, fix the UVs, import them back and try again.

I'm not sure why you chose to go about it that way. Exportation of the the skin weight maps is only necessary if you're going to detach the skin from the skeleton, and then re-bind it later. Did you do that, and just forget to mention it, or did you not do it?

So you know, you don't actually have to detach. You can adjust the UV's while the model is still rigged. It's hardly the recommended approach, but you can do it, as long as you don't perform any operations that might conflict with the existing history. Be sure to delete non-deformer history very often, as you work, and absolutely remember to do it at the end. The only history that should still exist when you're done is the deformer history (so the skeleton can function).

To avoid conflicts, it is often better to make a copy of the model, make your UV changes on the copy, and then after you're done, copy the UV's over to the original. This way, there's far less chance for things to get borked, since you're only making one big change to the original, instead of a million little changes. You'll still need to delete non-deformer history afterward, of course.

Lutricia Roux wrote:

Q1: This step puzzles me, should this really be possible, isn't the skin weights reliant to the UVs and the actual rig would be destroyed now by me editing the UVs after the actual weight painting?

If you altered the UV's on the model, then the old weight maps should no longer have been applicable. Something must be missing from your description of what you did. Did you perhaps add a second UV set? If so, you could have kept one set for weight mapping, and used the other for texturing.

This, just as above, is another example of where making a copy of the model could have been the best solution. After the UV changes were done, you could have copied weights from one model to the other. The Copy Weights function doesn't have to care about UV's, and since you weren't altering the actual geometry of either model, you would have gotten a perfect 1:1 projection from one to the other.

Lutricia Roux wrote:

Q2: Do anyone have an idea of what it is that makes Maya crash on export like this? I never experienced similar.

Without examining your scene file, I can make some educated guesses as to what might be going on.

My first guess is the one I already mentioned. Perhaps you've got multiple UV sets in place, and the exporter doesn't understand the structure.

Another possibility is that in having done so many things out of the typical order, you may have created a mathematical impossibility somewhere, which Maya is unable to resolve for export.

Every Maya scene, under the hood, is a large database of equations and variables. When you perform operations out of order, and especially if you don't delete history at the right times as you go, it's easy to create paradoxical situations, in which the math simply can't work anymore. I probably don't have to tell you this, but to avoid such problems, you should do things in the expected order.

If you find you need to make changes later that go out of order, whether because you forgot to do something or just because you changed your mind about something, you should take whichever path is least likely to cause conflicts. If I were to find myself in a situation in which I needed to alter the UV mapping and material assignments of an already rigged model, here's how I would handle it:

1. Make a copy of the model. Set it invisible, so it can't be messed with, and leave it alone, for now.

2. Detach the original skin from the skeleton. Delete history.

3. Make the needed changes to the UV map. Delete history. (Note: This would be a really good spot for an incremental save, if you haven't been doing them regularly all along. Save the scene as a new file, with the same name, but with a number after it, such as _001.)

4. Make the needed changes to the materials. Delete history. (This would be another really good place for an incremental save (_002).)

5. Bind the skin to the skeleton.

6. Make the copy visible, and copy weights from it to the original. (_003)

7. If you're satisfied that the original is now functioning properly in all respects, delete the copy, and clean up the scene. (_004)

8. Now you can safely export, and upload.

Of course, it's also possible that the scene file simply got corrupted, through no fault of yours at all. It happens. Either way, it's crucially important to do those incremental saves regularly as you work, so that if and when there is a problem, you can step back to an earlier version of the scene, from before the problem existed. That way, you only have to redo some of the work, instead of all of it.

Lutricia Roux wrote:

Q3: Suggestions of things to try to enable to export, is it my computer lacking enough memory, can I alter some settings in Maya etc?

I think it's unlikely that the problem has to do with computer memory or Maya settings.

Since the weight maps worked when they shouldn't have, and since problem started after material assignments, my best guess, again, is that you've got multiple UV sets in place, and possibly something in your shader networks is royally messed up, as well.

If you want to try to save the scene, I'd suggest you dig deeply through your UV set editor, hypergraph connections, outliner, and hypershade, to look for anything that might be out of whack. If you find anything at all that doesn't absolutely need to exist, nuke it. If you find any improper connections, break them, and reestablish them correctly. Etc., etc., etc.

Of course, this assumes that you already know what all the correct structures should look like in the first place. If this kind of thing is beyond your knowledge or comfort level, don't attempt it, because if you don't know exactly what you're doing, you could easily make things worse. It doesn't take much to utterly destroy a Maya scene, if you just start poking it with a stick.

Sometimes, the best solution is simply to start over. You mentioned the model isn't terribly complicated. Chances are it won't be difficult for you to recreate, then. And the good news is you're all but guaranteed to do a better job of it this time around, since you're now intimately familiar with what mistakes not to make. You'll certainly UV it, and get all your materials in order, before you rig it this time.

Lutricia Roux · January 29, 2013

First, a big thank you for these advices, they are incredibly helpful to achieve a effective and structured workflow for future projects!

Chosen Few wrote:

Lutricia Roux wrote:

I export the skin weight maps, fix the UVs, import them back and try again.

I'm not sure why you chose to go about it that way. Exportation of the the skin weight maps is only necessary if you're going to detach the skin from the skeleton, and then re-bind it later. Did you do that, and just forget to mention it, or did you not do it?

So you know, you don't actually have to detach. You can adjust the UV's while the model is still rigged. It's hardly the recommended approach, but you can do it, as long as you don't perform any operations that might conflict with the existing history. Be sure to delete non-deformer history very often, as you work, and absolutely remember to do it at the end. The only history that should still exist when you're done is the deformer history (so the skeleton can function).

To avoid conflicts, it is often better to make a copy of the model, make your UV changes on the copy, and then after you're done, copy the UV's over to the original. This way, there's far less chance for things to get borked, since you're only making one big change to the original, instead of a million little changes. You'll still need to delete non-deformer history afterward, of course.

Actually, I'm not sure either. I believe I had a major "brain fart" plus that my memory fails me which doesn't make it easier to clarify my odd actions. What I didn't know though, was that it was possible to edit UV's on a rigged model. That may been the reason too, I was trying to fix what I thought was broken after my UV editing (detach, attach and import skin weight maps) but instead adding even more problems. This is good news and great advices. I knew about the option to copy UV's but never thought of approach it this way.

Chosen Few wrote:

Lutricia Roux wrote:

Q1: This step puzzles me, should this really be possible, isn't the skin weights reliant to the UVs and the actual rig would be destroyed now by me editing the UVs after the actual weight painting?

If you altered the UV's on the model, then the old weight maps should no longer have been applicable. Something must be missing from your description of what you did. Did you perhaps add a second UV set? If so, you could have kept one set for weight mapping, and used the other for texturing.

This, just as above, is another example of where making a copy of the model could have been the best solution. After the UV changes were done, you could have copied weights from one model to the other. The Copy Weights function doesn't have to care about UV's, and since you weren't altering the actual geometry of either model, you would have gotten a perfect 1:1 projection from one to the other.

I agree, this was my understanding and part of the reason I got totally confused. I must have forgotten an important step here, but at least that is clarified, it should not work to import the skin weight maps to an UV set that I edited after the export. When you say it, it just dawn on me, why didn't I think of this! I should have copied the skin weight instead, I knew that it didn't care about UV's instead the actual geometry, but it never dawned on me until you mentioned it here. Anyhow, this is as I said before, great feedback and reminder. There are some other problems I had that I now can go back and fix in other projects!