MHX new rig hieralchy cause bad deform when switching about Forarm twist

[engetudouiti]

I found ti with g8 then now try with G3, then it seems clear , it need to be solved.

In this pic I just convert G3 as MHX then only move IK hand, around.. then now switch to FK. (snap FK arm to IK arm)

before

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snap IK to FK

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It is not small deform cuased by switch, so is need to be solved, even though it may not perfect same what Thomas plan .

To solve it, at first need to detect which constrain cause issue, and it is clear .

１　The copy rotatoin constrain which added for the forarm.twist.L is matter. then we should remove it. or you may test temporally hide the constrain. and snap IK to FK FK to IK again, strange problem never happen]

２　at same time after remove constrain,, when we twist forarm twist bone,, hand not follow , you may not hope it. to solve issue there are some ways most simple one is , directly add constrain for the hand.twk.L /R which can follow the twist arm bone rotation but keep move free (twist)

then add constrain “copy rotation” for hand.twk.L /R target bone forarm.twist.L like this

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Then actually reset pose, and try same thing again.

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you may never see such hard twist happen when snap FK IK

at same time, we may hope to twist forarms as same as daz for FK IK both mode. so I may recommend add shape for the hidden deform forarm.twist.L and R, so user can twist forarm. with both mode.

At current , it is not pefeclty same, because for IK chain (I suppose) bend bone need to twist with twist bone.. but untill try to make it work as same as daz,, we need to remove such deform first and anyway can twist forarm witout make things more complex.

Later try if you can use another bone to controll the twist.

I suppose you can clear devide deform bone, and twist or bend pose bone. but those things may better untill confirm it solve those issue first, because it actually make animation more difficult.

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[Thomas Larsson]

Copying the hand twist to the forearm was a trick that I learned a decade ago, and it seemed cool at the time. Now I realize that it complicates a lot of things, and adding the extra tweak bone makes things worse, so I removed the constraint altogether. Now the forearm is free to rotate around the y axis, and the hand rotation has the daz limits. Thus the tweak bone is unnecessary, and fk-ik switching seems to work well again.

[engetudouiti]

Thomas Please see another topic about twist things,, Alessandro made.

I beleve without use this, you should solve both problem at least for hand chain.

(only twist , twist bone correctly, when you twist cover bone . (I add pic and how you need to set for twist and bend constrain, clear)

I believe it is current best way, what I can suggest. I described all step.

https://bitbucket.org/Diffeomorphic/import_daz/issues/483/g3-g8-twist-bones-for-mhx

you actually test and set same constain please.. (and check snap FK to IK ,and actually rotate and confrim only twist bone twist .

[engetudouiti]

I add new way which solve another twist issue too. so hope Thomas try the way first. (hen this topic may need not any-more)