Foreword: I picked up Blender like a week ago, tops, specifically for this model.

Summary: I want to take pre-existing weights from one half of a model, and mirror them to their counterparts on the other side of the model. Not painting new weights, which is the only thing I could find info on.

I'm working on fixing a model for XNALara because it's the only one of its kind and its rigging is 20 flavors of messed up on the right half. However, no amount of googling or experimenting with any and every "mirror" or "symmetry" related option I can find has helped me replicate the "mirror painting with .L and .R bones" effect with existing weights.

This was something that was incredibly easy to do in 3ds Max when I had access to that in college, so the fact that I can't find any instruction on doing it in Blender baffles me slightly. What am I missing?

  • $\begingroup$ Half of your model has weights and the other doesn't? And you model is symmetrical? $\endgroup$
    – Leander
    Apr 27 '19 at 21:35
  • $\begingroup$ You could upload your .blend file to blend-exchange if you want us to look at it. After that, use the edit link below your question and update it with the link you got from blend-exchange. $\endgroup$ Apr 27 '19 at 22:11
  • $\begingroup$ @Leander: The right side HAS weights, but they're scrambled. $\endgroup$ Apr 28 '19 at 15:54
  • $\begingroup$ @metaphor_set: I was hoping to avoid that, since the model's... well, it's not NSFW but it's not innocent. Is that kind of content still okay to post? $\endgroup$ Apr 28 '19 at 15:54
  • $\begingroup$ I'm assuming that they're named correctly ("foot.L", "foot.R") and the vertices are symmetrical. Then you can just use the Add brush with weight/value of 0 and a strength of 1. Select a correct vertex group (x-mirror turned on in weight painting), go to wireframe of see-through mode and generously weightpaint over the existing ".L" weights. They should be mirrored (strength: 1) although unchanged (weight:0). Does this work for a single pair of groups? (Then I can share a script, that mirrors them automatically.) Or have I misunderstood your setup. $\endgroup$
    – Leander
    Apr 28 '19 at 16:20

If you have the bones named as Leander suggests (i.e., a left and right side naming convention and all needed bones in place), you can delete one half of your model (the half with the weights you want to copy), and then add a mirror modifier. Move the bones on the mirrored side around to see if it's working correctly, then apply the modifier. The only time this won't work is if you have shape keys on the model, since you can't easily remove modifiers on a model with shape keys.


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