Single Axis IK Tutorial

(harkyman) #1

Here’s a pdf tutorial (S68 inspired me to finally make one) about my technique for allowing an IK chain to move through only a single axis. It should be quick reading, and there are lots o’ pictures…

Here’s the pdf (96k)

Here’s the finished blend file as shown in the pdf.

(paradox) #2

Thanks I’m getting quite a collection of pdf tutorials. Also thanks for the subject just what I needed for my next project.

(iluvblender) #3

thanx for the tute dude.


(S68) #4

Oh boy, that’s usefull!!!

I got crazy in placin Empties as viewpoints for pose mode to fake a axis constrain like this… I’ll play with this ASAP



(mthoenes) #5

Great Tut,
Would be an excellent addition to the Blender Char Site… In my opinion.

(S68) #6


I’m really stupid… I forgot to de-parent the Leg.Acc…

I self-censor my question


you mean that Toe has an IK constrain and the target of the constrain is Leg.acc, right?

Did this (In armature every bone is IK to its parent EXCEPT Hip and Leg.acc)

But, in pose mode, when I move the Leg.acc bone the armature does NOT follow exactly. It follows at a certain distance :frowning: :frowning: :(, and the constrained joint is linked to the Leg.acc bone via a light cyan dashed line.

I was used to do IK with empties, which never yelded this. What an I doing wrong?

Needlesly to say, from top view everithing is spoiled by this behaviour.


/me feels stupid



(harkyman) #7

Nah. Sorry. I assumed that everyone did their IK chaining the same way, i.e. accuators housed within the armature so their are setable with Action keys. Here’s how I build one:

Point of origin - bone 1 (hip) - extend bone2 (up) - extend bone3 (mid) - extend bone 4 (low - this is the last actual bone to be used for deformation) - extend bone 5 (toe - this bone is only a “holder”, as the IK will work from the root of the last bone, not the tip) - stop - select the root of bone 5 (toe) and snap the cursor there - add a new bone to this same armature, bone 6 (Leg.acc).

Leg.acc should have the exact same root position as the root of bone 5 (toe) and the tip of bone 4 (low). You then enter pose mode, select bone 5 (toe), add an IK Solver constraint to it, Object: Armature; Target: Leg.acc.

The advantage to putting the control objects inside the deformation armature is that you can key the thing as a whole, allowing you to save the full motion as an action and make use of it easily in NLA.

If this description doesn’t suit, you can always download and examine the .blend file.

(S68) #8


got it by downloading blendo…

sorry… your tut is great :slight_smile: