It often is helpful to define transformations or other animatable parameters of an object as being dependent on transformations or other parameters of another object.

This can be done with expressions, as we've already seen.

Motion hierarchies provide another method of creating such dependencies.

In motion hierarchies, objects further up the hierarchy become the ``parents'' of ``children'' beneath them on the hierarchy.

The local frames of reference for objects at lower levels of the hierarchy inherit the transformations applied at higher levels.

Local transformations then are effected with reference to the inherited, transformed position.

Inverse Kinematics (IK) is a method by which reasonable positions and joint angles are determined algorithmically from the Cartesian space goal or position of an end effector that is located lower on the hierarchy.

Inverse kinematics often are used for animating character motion.

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This file was last modified on September 18, 2000.