When you animate characters (whether humanoid or otherwise), 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:
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 or intricate mechanical animation.
One of the most useful tools in producing computer animation is the ability to link objects together to form a chain. By linking one object to another, you create a parent-child relationship. Transforms applied to the parent are also transmitted to child objects. A chain is also referred to as a hierarchy.
The default method of manipulating a hierarchy uses a technique called forward kinematics.
Inverse kinematics (IK) is a method of animating that reverses the direction of the chain manipulation. Rather than work from the root of the tree, it works from the leaves.
Once you have set up a hierarchy using the Select and Link command or a system such as Bones, you can manage it using the Hierarchy panel.
