Preparing for IK

There are some things we need to do before we add the IK constraint. We need to adjust the bones that will be in the chain and add some new bones for the IK system.

Pre-bending IK chains

The IK constraint isn’t very smart – take a look at Figure 6.2 and notice how the elbow bends the way we expect it to. Chances are that the IK constraint will choose to bend the elbow the wrong way just because it has no concept of a human elbow.

Thankfully, there’s a way for us to show it how to bend and it is pretty simple. We take the arm bones into Edit Mode and give it a slight bend at the elbow. This preexisting bend tells the IK what direction it should bend in when animating a movement.

Figure 6.3 – Elbow bend

Shown in Figure 6.3 is the little bend I gave the bones by grabbing the elbow joint in Edit Mode and just sliding it toward the back of the arm a little.

Adding control bones

We’re going to...