Mocap Retargeting Recommendations

I am trying to re-target some mocap onto a humanoid that his multiple arm limbs. Like 4,6, 8 arms, etc. I’m not so familiar with mocap retargeting so I’m wondering what the best approaches are. I’ve looked into HumanIK and retargeting works great on normal humans in my tests. I suppose I could try to copy the animation and have the extra arms be offset from the original animation.

I’m wondering if there are better approaches though. Can HIK be extended to accommodate extra limbs? Are there resources where I can learn about how more advanced retargeting can be done so I can maybe write my own solution? Like how is HIK doing it’s retargeting under the hood? Or does there already exist software that has these features built in? I am pretty new to mocap and retargeting so I probably am overlooking some things that might be common knowledge in this realm. Thanks for any help

The non-coded approach I found worked for me was to retarget to the rig using HIK as a middle man, than transfer the (FK) animation to any arm in excess of the two you have in the mocap, from the original MOCAP arms. Then in Anim you can delay/ edit the additional arm anim.
However this is just my experience coming from an animator’s perspective, the practicality of it depends on the scope of your project. I made a tutorial about retargeting through HIK a few years back. It does not cover more than two arms and I am sure at this stage you’ll find a lot of the same info around on the web.

Short answer would be get as much working with the HIK rig and then use constraints to transfer the other limbs rotation, unless the other limbs are doing something more complex then making a simple IK rig that can manage the offsets.

I ended up doing this, although I am writing some custom logic now because some of the limbs are too anatomically different to do a direct constraint. Some of them look good just with constraints though. Thanks for the insight!