How do i set up simple IK Bones?

Hello there (:
I’m doing some rigging at the moment that i can’t achieve with Rigify because… it’s an animal i’m rigging and has a few extra joints and what not.
(And i have a problem with my computer at the moment to where i can’t load/download a single video that isn’t on youtube… and yeah i’ve tried other browsers, flash updates, html5, clearing cache, cookies, scans, disabling hardware acceleration, and what not…) so that’s why i’m asking here d:

I want to know how to set up IK on some bones in about the same way an arm works from Rigify where i can grab the hand and move it that automatically bends the bones in the arm as needed and have them face an elbow controller.

is that difficult to expain?

Thank you (:

You generally need an IK target bone, which is NOT part of the bone chain you want to control. It should be parented (disconnected) to the base, or the root of the whole armature.


Then, in pose mode, select the last bone in the chain you DO want to control (in this case the second bone), and add a bone constraint (icon is a bone+chain link). One of the options on the bone constraint menu is IK constraint.


In the IK constraint panel, select the armature as Target, then you’ll be able to select a specific bone, which is the IK Target bone you added earlier. Set the chain length to the number of bones in the chain that particular IK target bone will control. If you leave it at zero it will control everything in the armature – not recommended.


That should get you started.

Oh, it’s generally good practice to set up the bones in edit mode, so they don’t move when you switch to pose mode and the IK gets activated. (Unlike what I’m showing you here…I did that so you can see the parent relationship line between the IK Target and the Base bone.) So the IK target bone is generally placed at the end of the IK controlled bone chain, even though it’s not parented to it. It will still work if you don’t do that, but it will make you twitchy when you start to animate (the animator, not the rig).

Sorry for the delayed response there, my internet cut out for a bit.

That is very helpful and the pictures especially helped my understand it and get it to work xD

It’s kind of fun being able to set this up myself rather than relying just on Rigify.

The only thing i’m wondering though is that if i say, put this into a tail sort of rig. when i pull the controller at the end of the tail forwards, i can’t control which way the tail bends and it twitches alot trying to decide which way. i thought i could make a bone off to the side to be the pole target but that seems to break the rig so that none of the bones in the chain bend at all.

You can, but the set up seems to be rather odd. Might be a bug. When I added a pole target to an existing IK constraint, the rig broke. The controlled bone chain straightened out and didn’t respond properly to the IK Target position. However, when I deleted the IK constraint, and set it up from scratch, adding the Pole Target at the same time as I added the IK Target, it worked as advertised. Very Strange.

You may just need to change the Pole Angle value in the IK constraint. The default 0 is only right about 25% of the time in my experience. Depends on where all the relevant bones are pointed. You just have to experiment with values. Try in increments of 90 or 45 degrees. I think the most common values I end up at are 180 or -90 degrees.

It seems that when you set up the pole target, it uses the wrong Axis to look at the pole with. So even when i change the degrees of the offset, all it does is spin the bones rather than pull the tail ends of them towards the pole.

i wonder if i could use the IK without the pole for a long neck (i’m making a dragon if i didn’t mention that) because the neck of it wont be moving around so much so the IK might work for that… and then perhaps i could use something i’m hearing about called a Spline IK with hooks for the tail. I’ve just never really used curves for much of anything so i wonder how difficult they are to keep them apart of a rig s:

It won’t pull toward the pole. What you want to accomplish when you’re fixing the pole angle value is to get the IK chain to return to its original rest pose, where it was before you added the pole target.

For a long neck with IK, I would recommend one of two ways:

  • Don’t use a pole target. Use the IK rotation constraints. They’re not a regular constraint; they’re under the Bone Data tab in the Properties window, in the section labeled “Inverse Kinematics.” You can lock axes on each bone in the chain, limit the rotation on various axes, and thereby set it to only move in the directions you want to allow.
  • Don’t use Spline IK. It’s much more trouble than it’s worth. Use this instead if you want to go that route. Works well for necks, tails, tentacles, worms, etc. TailDemo.blend (423 KB)

I really like that TailDemo you have set up there d:

But i can kind of see, while messing with it, what you mean by it being a hassle for animation.

So i have been trying to tweak it a bit to see if i can come up with something cheeky.
First i tried making a separate chain above that tail you made and gave it the IK constraint like they showed me at the beginning of this post. And then i added Child of Constraints to each of the T1-T4 bones you had having them follow different bones in the chain above it. The idea behind that was that i could use the IK tail an use your T1-4 bones to tweak small segments in the tail. It worked for the most part, but i was still concerned about how jumpy and glitchy the regular IK tail is. So like you said i could go in and add in some Rotation limitations perhaps now that i remember it. i’ll try that next.

But the next thing i did was to have the T1 have a child of constraint to T2 with an influence of .750 and then give the same to T3 being the child of T2. I left T4 alone though.
What this seemed to do is that i could ignore T1 and T3 for the most part and just move T2 to get nice bends in the tail and then use T4 for an extra little curl at the end of the tail or as a head if this is to be used on the neck. Then on top of that i can add an extra controller above T4 that has T2 being a child of it by about 0.333 so that i can just move that last controller to have the tail move around and still have the extra curve of T4

idk d:
lol i’m getting all creative here now xD

Hmmm. That is a creative approach. I would not have thought to try that. I’d like to see the result when you finish tweaking it.

Here’s the contraptions as of right now if you wanna look at them. It’s mostly a matter of deciding which one works best for the kind of animation it will be doing i think. like. They could each work, but it depends on the person’s choice of workflow.

TailDemo.blend (569 KB)

Oh, I like that second setup, with the duplicates and the long IK chain controlling all the targets at once. It has a serious problem of pose-popping though. That’s partly to do with the long IK chain, but also to do with my incredibly lazy straight line IK chain. I’m going to play with your improvements and see if I can improve your improvements. :stuck_out_tongue: