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I have an exported model from 3ds Max, it was rigged with CAT. The main problem is that the CAT skeleton has lower arm roll bones that linked consistently (UpperArm -> LowerArm -> LowerArmRoll -> Hand).

That's how it looks

So, i don't understand how to make IK rig properly, because that hierarchy obviously screws up IK solving.

Any thoughts? I'd appreciate any help.

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  • $\begingroup$ Ccould you please give more details, for example what does it do that you don't want? If you want to constraint the rotation of some of the bones, you can select the bone and in the Properties panel > Bone > Inverse Kinematics, give some Limits $\endgroup$
    – moonboots
    Commented Sep 11, 2019 at 9:42
  • $\begingroup$ Well, my problem is that the roll bone obviously bends when IK is applied. I'll check the limit section, thanks for advice. $\endgroup$ Commented Sep 11, 2019 at 10:14

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So if you're trying to limit the rotation between the 2 lowerarm bones, what you're looking for is probably the IK Limits: In Pose mode, select the bone you want to constrain, go in the Properties panel > Bone > Inverse Kinematics (this menu appears as soon as the bone is influenced by an IK), then limit on the axis you want, in that case X and Z.

As you mentioned, in 2.8 you can simply click on the Lock IK option (top of the same menu).

enter image description here

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  • $\begingroup$ Yeah, i just did what you show and it works like charm! Actually, i'm using Blender 2.8 and it has simple "Lock IK" button for each axis. I've also added "Copy Rotation" with one axis, so the hand bone rotates the roll bone. Thank you! $\endgroup$ Commented Sep 11, 2019 at 10:52
  • $\begingroup$ maybe you should dig into switching your armature to B-Bones display and segment your bones $\endgroup$
    – moonboots
    Commented Sep 11, 2019 at 10:55
  • $\begingroup$ Unfortunately, i can't make any fundamental changes to skeleton. What's the advance of using B-Bones? $\endgroup$ Commented Sep 11, 2019 at 11:19
  • $\begingroup$ it will allow to segment your bone and therefore twist it differently and bend it smoothly, but it needs some tests to make sure it's an advantage. If your character is rigid, maybe not $\endgroup$
    – moonboots
    Commented Sep 11, 2019 at 11:42
  • $\begingroup$ Briliant, been searching the entire day for a solution to this, in Maya was possible to use a Pivot point to move the effector point, but in Blender your advice seems the way to go. $\endgroup$
    – Arise
    Commented Jan 15, 2022 at 18:45

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