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Posted

Hey all,

I can't understand how and what is the IK. Like in a human skeleton having 3 bones on an arm for example and the same bones are copied above and below the arm for IK thats what i don't understand. Also what are the constraints used for IK? I read the reference but still things aren't clear enough for me. hope you can help me by a good guide or useful information. tnx in advance...

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Posted
Hey all,

I can't understand how and what is the IK. Like in a human skeleton having 3 bones on an arm for example and the same bones are copied above and below the arm for IK thats what i don't understand. Also what are the constraints used for IK? I read the reference but still things aren't clear enough for me. hope you can help me by a good guide or useful information. tnx in advance...

 

Controlling an arm (or any other limb) using "FK" (forward kinematic), the controls work from the top down...bicep to forearm to hand. Meaning that if you move the bicep, everything below it in the chain moves and if you move the hand, it doesn't affect anything higher in the chain (forearm and bicep).

 

If you use "IK" (inverse kinematic) controls, moving the hand will move the entire arm. "IK" limbs generally use the "kinematic" constraint on the end bone of a chain of bones, that will make the chain attempt to reach the IK target (which is generally another hand controller in the case of an arm). To keep the chain from twisting in ways that an arm or leg aren't supposed to move, the IK setup will use a few other constraints as well.

 

In A:M (after v13), you can set up the FK and IK constraints in a way where they will make the switch without the arm or leg moving. In FK, you make the IK controls move like the FK controls. Then, in IK, you make the FK controls move like the IK controls.

 

I have attached a ZIP containing cut-down versions of the arm and leg setup from the Squetch Rig as examples.

 

Hope that helps, Muster.

v13_IK_FK_switch_examples.zip

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