Hierarchies and Forward Kinematics

Bipedal figure with part of its hierarchy diagrammed in the background

One of the most useful tools in producing computer animation is the ability to link objects together to form a hierarchy. By linking one object to another, you create a parent-child relationship. Transformations applied to the parent are also transmitted to the child object. By linking more objects to both parent and child objects, you can create complex hierarchies. Chains can be created to include ancestors (parents’ parents) and descendents (children's children).

Kinematics describes the movement of the chains. They can be animated by transforming the parent object (forward kinematics or FK) or by manipulating the other end of the chain (inverse kinematics or IK). Forward kinematics is primarily based on rotational keys; inverse kinematics is based on translations and rotations of special manipulators (nodes, goals and end effectors) which drive the ends of the chains.

Linking objects together and building complex hierarchies have the following common uses:

These topics explain how to plan and build linked hierarchies. They also show how the standard hierarchical linking commands are used to set up complex motion and to create jointed structures.

About Hierarchies

Manipulating Hierarchies with Forward Kinematics

Linking Strategy

Linking and Unlinking Objects

Selecting and Deselecting Hierarchies

Viewing Hierarchy Structure

Using Dummies

Adjusting Pivots

Adjusting Object Transforms

Locking Object Transforms

Changing Link Inheritance

Animating Hierarchies

Animating Links

Animating Attachment