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Issue with ik when character turns

Posted: Sat Sep 13, 2025 1:54 pm
by farenzzzzno
Hey everyone! Working on my first rig.
Any ideas why isn't IK working on this leg? Works perfectly fine on the other leg but if i turn my character the ik moves away from the bones, and does not work properly
Thanks!
https://drive.google.com/file/d/1D9aQrQ ... p=drivesdk

Re: Issue with ik when character turns

Posted: Sat Sep 13, 2025 4:45 pm
by synthsin75
Probably a bone inadvertently keyframed in the turn action.

Re: Issue with ik when character turns

Posted: Sat Sep 13, 2025 5:25 pm
by farenzzzzno
I checked the keyframes from the turning action, but there aren’t any strange keyframes in the IK bone or the leg bone.
When I turned the legs, I did it by moving their IKs. I’m not sure if that could be the problem. I just can’t figure out why it only happens to that leg
Can you show me, like, with an example of how can I fix it?

Re: Issue with ik when character turns

Posted: Sat Sep 13, 2025 5:59 pm
by Greenlaw
Hi!

I agree with Synthsin75; it looks like a conflict in one or more Smart Bones.

Can you post the project? You can remove the artwork if you wish, as it's likely that only the bones are needed for troubleshooting. Otherwise, it's just a guessing game.

Re: Issue with ik when character turns

Posted: Sun Sep 14, 2025 1:21 pm
by farenzzzzno
Here it is, Moho file.
Hope you can help
https://drive.google.com/drive/folders/ ... Rk0_aXHarJ

Re: Issue with ik when character turns

Posted: Sun Sep 14, 2025 1:27 pm
by synthsin75
None of the turn actions have any other bones keyframed, so I can't see the problem shown in your video.

Re: Issue with ik when character turns

Posted: Sun Sep 14, 2025 2:21 pm
by farenzzzzno
I'm trying to animate a walk from the side view of my character. The problem is that when I turn my character to side in the mainline, and then I move the ik anywhere, it doesn't work correctly.
In the video, when I turned the character, I moved the ik upwards to show that the ik was moving away

Re: Issue with ik when character turns

Posted: Sun Sep 14, 2025 4:12 pm
by Greenlaw
Hi Farenzzzzno,

I didn't have time to look deeply, but at a glance, it seems you have many bones, including other smart bones, under the control of GIRO CUERPO. In the image below, Moho is highlighting all the bones controlled by GIRO CUERPO.

Image

I mainly suspect that the rotation of the thigh bone is being 'locked' by the GIRO CUERPO Smart Bone because that's how it's keyframed, and this can make the IK appear to be broken. In other words, the IK is fine, but the Smart Bone is overriding the leg rotation.

My guess is that your intention was to keyframe only the X movement of some bones in the Smart Bone, so you might want to check that.

For example, here in the GIRO CUERPO Smart Bone timeline, I see rotation keys for the Thigh and Shin bones, and the Thigh bone is keyframed to stay between 180-182 degrees (pointing downward.)

Image

This makes the IK do this in the Mainline...

Image

But after I remove the rotation keyframes to allow the bones to move freely, it looks like this...

Image

The above is more correct, but we probably want the leg to bend the other direction, which is a different issue. To correct this, we need to 'hint' the Thigh bone to bend in that direction, so it looks like this...

Image

To fix this, I made a slight bend in the knee at frame 0, which tells IK to bend the knee in this direction. It's not necessary to 'bend' the artwork to match; the bend is there only to inform the IK. Here's what this looks like...

Image

As you animate the character, you may wish to bend the knee in the other direction. To do this, keyframe the knee rotation to bend the other way, and IK will understand your intention. (It's typically two keyframes near each other: one to hold the pose for the first direction, and a second to transition the bend to the opposite direction.)

Tip: This is just me, but I generally don't use Smart Bones to control the transforms of many bones in my rigs because that can limit the posing possibilities and make performances look mechanical. (Which is fine if that's the intention.)

I suspect there's more to fix here, but I hope this info gives you clues for where to look.

Good luck!

Re: Issue with ik when character turns

Posted: Sun Sep 14, 2025 4:29 pm
by Greenlaw
One more tip: it's a good idea to name all your bones. I like to keep the names short and clearly descriptive.

For example, when I name my right leg bones, I typically call them...

Leg Up R
Leg Lo R
Foot R
Leg Tgt R

This may seem like extra work, but it pays off by making editing and troubleshooting rig issues much easier.

Re: Issue with ik when character turns

Posted: Mon Sep 15, 2025 4:54 pm
by farenzzzzno
Thank you!! Thanks, Greenlaw and Synthsin75, for your super help :D ! It solved my problem.
By the way, I was wondering if either of you could give me some feedback, corrections in DM on some animations I'm working on, I’ll have them ready in 3–4 weeks and can send them to you if you’d like. Thanks again

Re: Issue with ik when character turns

Posted: Mon Sep 15, 2025 7:08 pm
by synthsin75
Greenlaw is the expert animator, but I'd take a look if you want a second set of eyes.