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In this tutorial, I'll introduce you to animating characters with an IK rig.
As you may have noticed when posing the pyro from the earlier tutorial,
it's easy to accidentally mess up the posing of a joint by adjusting one of its parents.
Let's break this on purpose by puppeteering some pelvis rotation on the pyro.
You can see that as I rotate, the head, hands, and feet are now all in the wrong place.
So I'm going to hit Esc to discard that modification, and this time, I'm going to lock the head rotation to the world,
so that when I rotate, the head's animation stays in the same orientation.
Select the pelvis, and hit the up arrow to go to the head of the shot, and get ready to puppeteer some pelvis rotation.
Hit the Spacebar... and hit Spacebar to stop.
Locking the orientation works fine for the head, but for something like the hands and feet, where the position matters,
we're going to need to drive the elbows and knees with inverse kinematics.
So let's create an IK rig. Right-click on the pyro's animation set, and look for the Rig menu, and choose rig_biped_simple.
This creates the IK rig. This only works for the skeletons of the nine player classes of Team Fortress.
You can make your own custom rigs and skeletons, but we'll go over that later. Now, let's take a deeper look at the IK rig.
You can see that the animation set controls are now color-coded and organized a little bit better.
And some of the joints are now hidden. You can right-click to show hidden joints if you need to.
In the viewport, if you hold down the Ctrl key, you can see that the skeleton now has elbow and knee pull-vector controls.
Once the motion is traced from the FK skeleton onto the IK rig, the motion gets deleted from the joints, and the IK rig becomes active.
The result is that the IK rig's motion looks exactly the same as it did before.
However, now, if we rotate the pelvis, you can see that the feet and hands stay put.
Note that if we rotate too far, or the IK control gets out of range, the joints driven by the rig will just point back to the IK controls.
This means you must animate the IK controls to stay within range of the limbs that they control.
So it looks like the feet and hand controls are in the right place on the first frame of the shot,
so let's put the playhead on that frame, and lock them in space. Select all the hands, elbows, knees, and feet, and lock them to the world.
And now, place the motion path on the tip of the toe, using Ctrl+middle-mouse-click.
This places the display path on the surface of the model, by the way.
Now, delete the counter-animation from the locked joints by applying the Playhead preset.
Notice that the motion path is updating. Go ahead and review.
And now you can see that when the pelvis is rotating, the feet are staying on the ground, and the hands are staying on the wheelbarrow.