What is IK?
A character Animation Rig is normally a combination of FK and IK setups. The spine, neck, and head, plus things such as tails, are normally set up as an FK. However, things such as arms and legs are normally set up as an IK within an Animation Rig. On more advanced Animation Rigs, it is possible to set arms and legs up in such a way that they can switch between the IK and FK, but that is beyond the scope of this book. Most of the time, you want a good IK setup for your arms and legs.
Understanding IK
Imagine we had an arm and a hand. We want to move the hand from A to B. With an FK setup, we will first need to rotate the upper arm joint and then the lower arm joint for the hand to reach B, as shown in Figure 15.1:
Figure 15.1 – FK A to B
In reality, we'll have to keep switching between rotating the upper and lower arm joints until we reach B exactly. This is a very time-consuming process. Very early on in the history of computer...
