Skin Weights Are Not Saving Properly

[Anonymous]

I'm trying paint weights in Maya 2020, but each time I modify the paint for a joint (shown below), when I click off weight paint mode and return I see the paint is randomised again, for instance random blobs on the head shown below when I only want to paint the left arm.

Also shown in the image, I have tried various settings including turning on/off max influences, turning on/off Deform User Normals, locking all other joints while painting one, and both Classic Linear and Dual Quaternion for Skinning Method. This is all to no avail. What can I do to fix this?

[stephenkmann]

from your settings image there, it looks like you have all the joints but 1 locked. 

This will not work. the weights (by default) are normalized, meaning they must add up to 1.00. 

so when you paint the weights. the values have to come from some other joint. if they are locked. than they won't move

I would suggest trying:

un-lock ALL joint's weights

turn off "maintain max influences" on the skin cluster. 

try using only "add" for painting the weights

double check you don't have overlapping UVs ( if so. fix them so they  are not overlapping)

[Anonymous]

I've tried the first 2 points you suggested and it didn't work, I'll try only 'adding' weights and I have not applied any UV textures yet.

[stephenkmann]

not textures.. UVS

the paint wts looks at uvs to determine where to paint. 

if you uvs are overlapping.. then it will paint in all the areas that overlap

[jmreinhart]

The UV's are used if you export using skin>export weight maps. But they are not used while you are painting.

[stephenkmann]

that has not been my experience. 

 I've often found students having trouble with painting wts, that fixing the overlapping uvs, fixed their issues. 

For a long time  the paint wts tool were directly affected by the uvs,  I think there are still some painting operations that use the UVs . 

Of course exporting and importing wts would do it.  But I've also seen files that were working fine for some time. saved, opened, saved , opened, saved , and on the next open the wts went haywire.. Fixing the UVs seemed to fix when this happened. 

Might as well start with everything clean so you can narrow down what the problem might be. 

hth