How does the mirror modifier work in relation to bone weighting?

so i’ve built and mostly rigged a model, and i’ve used a mirror modifier from the start. Which means technically only the left half of him exists.

I imported hijm originally from makehuman, and modified him very heavily. He came with a lot of vertex weightings done, but i’ve since transferred him onto a simpler armature and i’m redoiung those vertex weights.

What i’d like to know just now, is about how the mirror modifier affects vertex groups. For example, can i just go and delete all the “*.R” vertex groups, and assume that they’ll be remade by copying the left side versions when i apply the modifier?

Or do i need to keep those groups existing, and the information will be copied into them?

are they presently interfering with mirrored vertex weighting information? or are they just doing nothing right now?

hello ? :stuck_out_tongue:

hey , well test it ! :wink:

but if u have rigged it with the mirror modifer on the weight data will also be mirror , with means that u cant modify one side without the other getting the same data.

Hii x

I am testing it and using it now, but it’s difficult to see how some things work. It would help greatly to benefit from the knowledge and experience of you animation gurus <3 And i’m no doubt certain that there are pitfalls and pain points i’m going to run into, it’d be useful for someone to point out such things

Specific questions:
1.Does mirroring vertex weights require that an opposite-side vertex group be present ? (eg Shoulder.L and Shoulder.R).
2. If one isn’t present, will it be automatically created, or will the vertices on the opposite side not be weighted, or will they be weighted with the same group instead of an opposite one?

Yes, I believe you do need to create empty target vertex groups for the mirror modifier to assign things to. But again this should be easy to test. Just make a model with only left side vertex groups then apply the mirror modifier. Either it will create and assign right side vertex groups or it will not. The test should be pretty unambiguous.