Mirroring bone weights

Hello everyone! I have a question that I’m sure has a simple answer, but it’s eluding me.

So, I made a mesh using the mirror modifier and then I created the rig for it. Next, I skinned one half of the mesh using weight painting. Well, at the time I didn’t really know what is was doing in terms of mirroring the weight painting, so I didn’t have X Mirror checked. Is there a way to mirror or copy weights from one bone to the mirrored side of the mesh once they’ve been skinned? What I mean is, say I already skinned the right hand to Hand.R, is there a way to mirror that skinning to the vertices on the left hand to Hand.L? Or am I going to have to reskin the whole mesh?

I thought I saw a script for 2.49 that basically did what I need, but I can’t find any for 2.5.

Anyway, thanks in advance for any help!

OK, well, I solved my own problem.

Next, if you’ve made the mistake of skinning your model without using the Mirror X option for the weight paint, then delete your Mirror Modifier, you won’t be needing it.

Now, select your mesh in Object Mode and press Ctrl + D, then scale your mesh by -1 along it’s axis of symmetry. My model was a character facing along the Y axis, so I scaled -1 along the X.

If you do the previous step correctly (assuming you had Clipping selected on your Mirror Modifier to begin with), all the center vertices for these two object will be identical, this will make your life easier.

Next, go in to the mirrored object, go to the Object Data tab in the Properties Window and go to the Vertex Groups panel. Change all of the vertex group names from WhateverBoneName.L to WhateverBoneName.R, or vice-verse depending on what side you mirrored. Now, all the vertex groups on the left side object should end in .L and all the vertex groups on the right side object should end in .R. Remember to make sure your bones are named accordingly as well.

Next, Shift Select both objects and press Ctrl + J to join them. Your Normals may be confused here. Just select all your faces in Edit Mode, press Ctrl + N. If your model is still looking strange now, select all the faces again in Edit Mode, press W then select Flip Normals. Now it should look alright.

Last step is to select all your faces in Edit Mode one last time, press W and select Remove Doubles (Told you having those center vertices at the same place would come in handy :slight_smile: )

And that’s it. A bit tedious, but it works. Hope this helps someone else!