6.11 INVERSE KINEMATICS

Whenever you decide to switch you computer on, you just push the power switch with your finger-tip. Let's analyze from animator's point of view, what happens when you switch your computer on.

All kinds of muscles in your shoulder rotate your upper arm around your shoulder. Also your biceps rotate your forearm around the elbow. Finally muscles in the forearm bend your finger around its joints so that your finger-tip eventually pushes the button, This means that the position of your finger-tip is determined by the positions of the bones between the finger-tip and the shoulder. In other words, the way your muscles modify the bones makes the finger-tip hit the power-switch.

This is not how Inverse Kinematics works. When using Inverse Kinematics, you don't have to define how the bones should be rotated in order to produce a desired route for the finger-tip. You just define the position or route for the finger-tip and Inverse Kinematics solves the problem, how the bones should be positioned.