Working with IK rigging

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When you're working with skeletal animation, the skeletal joints exist in a hierarchy: when you move the parent, you move the children. Thus, when you rotate the lower arm, the hand moves with it. But sometimes, you may want to move a parent joint without moving its children. For example, if the hand is holding a doorknob, you may want to leave it in place even if the lower arm rotates. That's when you use inverse-kinematic, or IK, rigging (as opposed to forward-kinematic, or FK, rigging).

IK rigging is a way to temporarily change the hierarchy of the joints, so that you can move only the body parts that you want to move, without affecting other parts further down the chain.

Note:You must unlock a character's animation set and all its controls before you can create a rig for it.

To create an IK rig for a TF2 character:

  • Right-click on the character's animation set, click Rig, and click rig_biped_simple. Note that the controls visible in the Animation Set Editor have changed. The original controls still exist, but they are now hidden. You can display them by right-clicking in an empty space in the Animation Set Editor, or by clicking the tools icon in the upper-right corner of the Animation Set Editor (SFM icon Tools.png), and then clicking Show Hidden Controls.
Note:The IK rig contains pull-vector controls for the character's knees and elbows.

Even though the model now has an IK rig, the existing animation is unchanged. However, if you rotate a joint control after applying an IK rig, you'll see that the parent relationships between the joint controls have changed.

Now that you've created an IK rig, you can rotate specific body parts (like the pelvis) without affecting the rotation of other body parts (like the hands and feet). You can lock also joint controls to the world in the Animation Set Editor to make sure they don't move when you rotate other joint controls.

To remove an IK rig from a TF2 character:

  • Right-click on the character's animation set, click Rig, click Detach Rig, and click rig_biped_simple.

See also