How to mirror weight paint properly?

[Healisoulus]

Grettings and happy New Year. I've got a bit of a problem with weight painting: I painted on the left side of the shorts, that weight paint is related to the left hip_twist bone, the one at the bottom. Now I would like to mirror this paint to the right side, make it so the right hip_twist has the same weight paint but mirrored. How should I do that, please?

Going through the discussions here, I found a post where someone recommended adding a Mirror Modifier. While I did get a "perfect mirror", only one of the two bones gets the weight paint. Here are a few screenshots for better understanding: https://imgur.com/a/kyni7Kh

[The Renderer]

You need to name the bones correctly:

https://docs.blender.org/manual/en/latest/sculpt_paint/weight_paint/tool_settings/symmetry.html
https://docs.blender.org/manual/en/latest/animation/armatures/bones/editing/naming.html#armature-editing-naming-conventions

Or do it like this (not sure it still works in 3.4):

https://www.youtube.com/watch?v=aIK1jjmupG8

[Healisoulus]

Publicado originalmente por The Renderer:

You need to name the bones correctly

Maybe I should have been more specific, but the bones have the following names: bip_hip_l_twist2 and bip_hip_r_twist2. According to the documentation you provided, these should qualify as "mirrorable". If it's still wrong, what exactly am I missing here, please?

If it helps, the model is an MDL file - a model for Source FilmMaker.

[The Renderer]

No, read it again. It needs to have a separator in the second or second-to-last character. So, e.g. hip_L or hip.L or hip left. Or L_hip etc.
You have yours somewhere in the middle.

Edit: Or in your case bip_hip_twist2_L (or .L or ...)

[Healisoulus]

I have good news and bad news. The good news is that I fixed the bone names and now the modifier works properly, so thank you. The bad news, however, is that Blender Source Tools refuses to export the model due to it apparently not supporting Mirror modifiers. Can I somehow transfer the mirrored weight paint onto the model so that it it sticks around without the modifier?

[The Renderer]

Can't you just apply the modifier?

I am not sure what you now did. Usually you don't use a mirror modifier at all and use the "Vertex Group X" checkmark for the left-right bone symmetries while weight painting.

[Healisoulus]

Publicado originalmente por The Renderer:

Can't you just apply the modifier?

Normally that would work, but my model has a few shape keys, and apparently I can't apply the modifier because of that.

Publicado originalmente por The Renderer:

I am not sure what you now did. Usually you don't use a mirror modifier at all and use the "Vertex Group X" checkmark for the left-right bone symmetries while weight painting.

Initially I tried to weight paint with X symmetry on, but it wasn't working correctly for me (I guess due to porr bone naming), so I decided to paint the sides separately. Not the most rational decision, I know :\

[The Renderer]

No, that's fine, it's just that weight painting is not my area of expertise either, much less Source, so I'm not sure how to proceed.

You could try this plugin to apply the modifier while keeping the shape keys but no guarantees it will work or help with your specific issue (better back up your blend file before trying):

https://github.com/smokejohn/SKkeeper

[Healisoulus]

Publicado originalmente por The Renderer:

You could try this plugin to apply the modifier while keeping the shape keys but no guarantees it will work or help with your specific issue (better back up your blend file before trying):

https://github.com/smokejohn/SKkeeper

Thank you, I tried it but it didn't work properly. I should have noticed earlier: adding the mirror modifier resulted in some of the central parts "merging" ( https://imgur.com/a/leXYlNL ). After a bit of further testing I have come to the conclusion that there are some symmetry issues with my model, which is probably why X-symmetry wasn't working properly in the first place.

Eventually I decided to brute-force it and simply painted the weights on the other side as close to the "correct" side as I could. And fortunately it worked well enough, so I guess the issue is resolved now.

P.S. That addon you linked was actually very handy when I had to apply a multires modifier. So thank you again.