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416 Chapter 12: Animation

Hier ar chi es a nd K i nemati cs

When animating characters, mechanical

assemblies, or complex motion, you can simplify

the process by linking objects together to form a

hierarchy (page 3–951) or chain. In a linked chain,

the animation of one member can affect some or

all of the others, making it po ssible to animate a

number of objects or bones at once.

The term kinematics (page 3–960) describes the

movement or animation of the chain. There are

two typ es of kinematics:

•Withforward kinematics (page 3–944) (FK)

, you transform a parent object to move its

descendants (its children, their children, etc.).

•Withinverse kinematics (page 3–958) (IK), you

transform a child object to move its ancestors

(its parent and so on up the chain). You can

also use IK 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 .