Reverse IKAs ... Er.. how?

Okay, I’m trying to learn reverse IKAs, and I’m following THIS tutorial.

I’m on the first step (of the correct thing to do) and he tells me this:]


Start a new armature. Make a chain if three bones - upper leg, lower leg and a null bone. The null bone is a small bone, that we’ll add the IK solver to. Now position the 3D cursor at the heel and add the foot bone. Now add the foot bone as an IK solver constraint to the null bone

Okay, firstly, WOW, that’s confusing.

I’ve got a chain of 3 armatures, as it says. Good. I’ve added a sperarate bone called “foot”. Fine. I click on the null bone, and add the IK solver there.

Now if try to move the foot, it affects the other bones, yes, BUT IT COMES OFF. It’s like it has some kind of weak magnetic field; it’ll make the other objects move, but they’re not in full contact with it.

AND, it says that I can move the upper leg and the foot’ll stay where it is. Heck no. If I move the upper leg bone, the whole shebang comes with.

So what the heck am I doing wrong?

Or is this just a faulty tutorial?

Or can somebody please direct me to one that acutally makes SENSE?

It is not faulty. I am as newbie as you, or a bit less… And i made it recently, that example.

It worked, though yep, the foot stays on the floor when you drag the root like for a jump…but that is said in the tut, that is the drawback, it is not a continuous armature, but at the heel starts a new one…

maybe these days is being thought to add certainnew feature (kind of joint pinning) for all these that may allow another type of armature, probably continuous…so, maybe is just a matter of wait fo rthat :slight_smile:

Anyway, when you add an IK solver, you have to put in “OB:” field the object over which actuates (an empty, or in this case, the Armature) , and a target, the bone (ie: Bone.001) that will actually move it all.

For example: I want an arm be ik moved by a floaing bone…Then I may select the whrist bone…add constrain…ik solver type…OB: Armature …target (the floating bone, if I remember well) and that floating bone will ik move the arm from the whrist (I hope I remembered well, this all is too new for me) But the weirdhat tut is much more complex than just ik solvers.

I got it.

It was the parent of the foot bone.

Changed to blank (no parent) and it’s working fine.


Reverse Inverse Kinematics?

Sounds like when someone says: I ‘aint doin’ nothin’.

Double Negatives! :wink:

To make this tutorial actually work, you need to do several things that weren’t really spelled out.

First of all, when you create the armature, you must parent each object to the “bone” that will control its movement. The pieces of the leg are parented to the corresponding bones. Otherwise those leg-pieces just stay right where they are as the foot moves, because they aren’t aware of any relationship between themselves and “'dem bones.”

(When an entire object is parented to a bone, the bone’s movements affect the entire object. When a vertex group is parented to a bone, the bone’s movements affect the vertices within the group.)

In addition to whatever bones you need to move pieces of the leg with, you need one more small bone whose purpose is not to move something, but to be moved by something. That’s what the “IK Solver” funny-biz is really all about: letting you move the foot, and Blender determines the position of the ankle, shin, and thigh to follow the foot.

Frankly-weird terminology like “IKA” only obscures the conceptually simple concepts that are working here. But unfortunately, computerdom is full of TLAs.*

  • TLA = Three-Letter Acronym :smiley:

Note: The term “parenting to” has the following meaning. Suppose I have an object that represents a waiter’s tray and another object that represents a glass of wine. If I make the tray “the parent of” the glass of wine, then the wine will follow the position of the tray whereever that tray goes. (Click on the glass, press Shift, then click on the tray, and press Ctrl+P, “Make Parent.”) In Blender-speak, I have “parented the glass to the tray.” The desired children are clicked first, then the desired parent, then Ctrl+P.