Forearm twist not working automatically when using only some old version ports, but not all.

[Calibrator]

Currently using 1.7.1.1677, updated to 1.7.1.1703 mid writing this post, issue persists. (even after pressing update mhx in the n menu)

When rotating the hand IK by the local Y axis the forearm isn’t following. This is happening currently on 2 out of 4 models I ported on a previous version of diffeo. I can’t remember which one. I’m not entirely sure if one of them was ported with this version or not either, it’s possible.

3/3 models I can remember and definitely ported with this version work fine.

I checked old renders and it looks to me like this wasn’t an issue before 1.7.1, I was also shocked to learn yesterday that the forearm bone didn’t follow the rotation.

In the event that you won’t try and fix this could you at least tell me how exactly the IK is made to rotate the lower arm twist so I can fix it myself? I’m only aware of constraints and it looks like that’s not the problem here.

[Thomas Larsson]

The mhx update tool has only been tested with the stable versions, and not very extensively with those either. It might a good idea to stick with the version that the mhx rig was created with. Or save a file with the original genesis rig and generate mhx again with the new version.

The left forearm twist is implemented with a copy rotation constraint on the forearm.L bone on the hidden layer 15.

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What probably goes wrong is the driver for the influence. It should look like this. If the path is red or Prop refers to an armature instead of an object, the driver value is always zero.

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[Calibrator]

Weirdly enough that seems fine to me.

Anything else I should look into?
Also I wanna add that it seems that this particular model has a significantly slower response time when doing anything with the rig compared to the other models, although not sure if that would help at all…

[Alessandro Padovani]

Added information on the mhx runtime to the wiki since I see this is a FAQ. Requires some planning when rigging figures.

https://bitbucket.org/Diffeomorphic/import_daz/wiki/Setup/Rigging

[Thomas Larsson]

I updated mhx rigs generated with stable versions 1.6.0, 1.6.1, 1.6.2, and 1.7.0. In all cases the forearm twist is controlled by the ik hand. The fk hand also controls the forearm twist in all cases, but for 1.6.2 and 1.7.0 you can turn it off with the Forearm Follows Hand properties.

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Moreover, the update tool crashed when I tried it, so maybe you only got a partially updated rig. The crash is fixed now.

[Calibrator]

Yes! Thank you very much! After updating the MHX rig I had to enable those 2 Forearm options and now it works as it should. Seems like the issue is solved.

[Calibrator]

Ah I may have realized what happened. When you import a pose and it switches to FK, when you switch to IK after that it doesn’t automatically enable these forearm follow buttons. I can’t confirm that was the problem in the first place but I just noticed this happen 2 minutes ago.