When animating characters, mechanical assemblies, or complex motion, you can simplify the process by linking objects together to form a hierarchy or chain. In a linked chain, the animation of one member can affect some or all of the others, making it possible to animate a number of objects or bones at once.

The term kinematics describes the movement or animation of the chain. There are two types of kinematics:

With forward kinematics (FK) , you manipulate the top of the hierarchy to animate the entire chain.

With inverse kinematics (IK), you manipulate an object at the bottom of the hierarchy to animate the entire chain. Frequently, IK is also used to make an object “stick” to the ground or another surface, while allowing the chain to rotate off the pivot of that object.

Forward kinematics is the most straightforward method for animating hierarchies. Inverse kinematics requires more setup than forward kinematics, but is more intuitive for complex tasks such as character animation .