This video shows my issue:
Anyone know how to fix the problem?
Thanks!
I am not sure why this is happening to you it should fold. Here is a similar setup (and it folds):
Bones.blend (140.7 KB)
Do you have any other constraints on the bones or rotation limits in the IK settings?
If not you could share a blend with just the bones to have a look at.
Edit:
The rotation limits for bones in an IK chain are set for each bone in this tab. Check that you have no limits.
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We’re looking at a 3-bone chain? You don’t want straight angle limits, you just want more stiffness. Select the final bone in the chain (since that’s the one that you want to be more stiff) and look on properties/bone/IK. Increase the stiffness values for X, Y and Z.
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I didn’t have any limits set, however, someone on Reddit pointed out that I can select the third bone in the chain and adjust its Stiffness value which would help the second bone to bend more, and that looks like it did the job.
Thanks for the help!
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You answered this right as I was posting my message about finding the answer on Reddit. Cheers!
Oh, jumped the gun… It’s partially fixed… When moving the foot handle, it bends properly, but when I move the Torso Handle, it’s still got the same issue:
Sorry, does anyone know how to fix this issue on both the top and bottom part of the leg? It works with the foot handle, but when I use the Torso handle it still won’t close. It looks like I need negative stiffness on the foot bone (yellow) because when I increase the stiffness it makes it worse, but you can’t go less than zero on the stiffness value.
It doesn’t matter where the parent is-- what matter is only the distance between the parent and the IK target. You can see this by posing the parent in a way that you’re unhappy with, and then move both the parent and the IK target together such that the parent is back in its original position, and see that the bends don’t change.
It’s hard to know what you want, and it would be easier to see what was going on if we had a file; it’s also kind of weird that you have the mesh in your pictures, but unweighted to your bones, and this might make it harder for even you to be sure what you want. In the case of the pic you’ve labelled as not fixed, we can see that the angle between the final bone and the second-to-last bone is more or less unchanged from rest, and that’s the only thing you mentioned as being a problem previously, so for me, and I think other people reading, we’re wondering, well, what is it you’re after?
However, if what you want is “negative stiffness”, then of course there’s no such thing, but stiffness is relative, so if you increase the stiffness of all other bones in the chain, that’s basically negative stiffness.
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In the example file I linked in my first post there is no angle limitation either way (moving the target bone or the Torso.)
There must be something that is creating that limit. As bandages says the best thing would be for you to share the file so we can have a look.
We only need to see that IK chain, you can delete everything (mesh’s etc) except the bones and save the file with the compress option (N panel in the save dialogue-or cog icon top right of the save dialogue.)
No worries, I solved the issue by removing the foot bones because I realized the way the mesh was designed they wouldn’t move anyway. For some reason having the 3 chain IK setup made the bone in the middle not bend as much. The reason I had the mesh in the scene was that I was in the process of rigging. Anyway, I came up with a workaround so good enough.
Thanks for the help.
In the first image that is working, the angle between the second and third bone is small. Maybe 5 degrees. But when I move the Torso handle, it won’t go beyond maybe 110 degrees. That was my issue. Anyway, I came up with a workaround. Thanks for trying to help.
Bugger. My workaround didn’t work because it causes the feet to move when you lift the torso. I didn’t notice until I skinned the mesh. So I had to add a foot bone in again, and now I’m back to my original problem. I’ve uploaded a blend file. I’ll try to explain what I want better…
The mesh is a sort of Spider Tank Mech - 4 legged walking tank.
I’m also restricted to one photo per post so apologies for multiple posts
And this is what I want to happen:
I basically want the limbs to act more like arms and hands rather than legs and feet. Think of a Praying Mantis.
I can’t upload a blend file because I’m new to the forums apparently, so here’s the file on my google drive: https://drive.google.com/file/d/1qX5yggjMzxqpn9AtpKhTFHEM4EPMI5T8/view?usp=sharing
The rig is only one leg because I plan to symmetrize it when I’ve got it working the way I want.
It looks to me like you want LowerLeg to do all of the rotation whenever possible. In your desired picture, Foot and UpperLeg have little or no rotation from their rest. We can get this simply by maxing out the stiffness on all axes on UpperLeg and Foot:
However, I suspect that you also want to limit the rotation that LowerLeg is capable of. Right now, all of your bones have no axis limits, and in weird positions, they’ll prefer rotations that they probably shouldn’t be capable of. I would recommend fixing the axes and setting up some IK angle locks.
I would also recommend working with an actual mesh attached to the bones. There are ways to move this that won’t look good, but when you have a mesh, you’ll see that the ways it doesn’t look good are ways that it will never look good, because the positions are out of range of the bones. For example, even with max stiffness, it will still extend all bones to reach the IK target, and the solution to that is, don’t move the IK target that far. And, because the first two bones combined are shorter than the third bone, there are some places where a certain rotation is required for when the IK target gets too close-- again, the solution is, don’t put the IK target in those positions.
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Yeah, that’s strange. I tried increasing the stiffness of the upper leg and the foot, but it didn’t seem to have any effect. You are right I will need rotation locks in place too. I just wanted to get the collapsing to happen before I worried about that.
Thanks for your help. I’ll play around and see what result I can get. Also, I’m less worried about the mesh since it’s a mech, every piece that moves is going to be hard-skinned and I put the bones in the exact same place as the mesh pieces so it should be fine.