2009

Defining a sibling in this way has the practical advantage of letting you, for
example, cycle through the selection of all finger links on one side of a
character without the selection jumping to the other hand. But cycling through
siblings with an arm object selected usually results in selecting the opposite
arm object.
When using these commands,
hidden on page 8002 and frozen on page 7989
objects can't be selected, but are considered part of the hierarchy when deciding
what is and is not a sibling. Also, if a selection filter on page 208 is active,
siblings that don't meet the filter's criteria cannot be selected. In all such cases,
ineligible siblings are skipped in favour of a further sibling, if any exists.
Customizing the Quad Menu
You can customize the
quad menu on page 7516 so it displays commands to
select children, or ancestors, or both. From the Customize menu, choose
Customize User Interface on page 7697. On the Quads on page 7704 tab, drag
Select Ancestor or Select Children from the list of all commands to the quad
menu. Then you can easily select children or parents with a right-click and
then a click.
Animating with Forward Kinematics
The default method of manipulating a hierarchy uses a technique called
forward kinematics on page 7987. The basic principles employed by this
technique are:
■ Hierarchical linking from parent to child
■ Placement of pivot points to define the connecting joint between linked
objects
■ Inheritance of position, rotation, and scale transforms from parent to child
You animate the objects of a hierarchy in much the same way you animate
anything else. Turn on the Auto Key button and transform members of the
hierarchy at different frames. However, you need to be aware of a few special
issues for animating hierarchies.
3354 | Chapter 15 Animation