9

Animating Links 431
Robot arms pass a ball from one hand to the other.
Adding a nd Delet ing Li nk s
YouaddanddeletelinksontheMotionpanel.
Expand the Link Parameters rollout and click Add
Link or Delete Link.
• Click Add Link then click the object that you
wan t to link to as a parent. The frame at which
youaddthelinkistheframeatwhichcontrolis
passed. You can change the link f r ame with the
Start Time par ameter.
• Click the name of a parent object in the l ist, and
then click Delete Link to remove the link.
Properties of the Link constraint include:
•TheLinkconstraintrespectsthelink
inheritancesettingsappliedtothechildobject.
• The object using a Link constraint is not a true
child object. It does not appear in the subtree of
any linked p arent objects.
• Objects with Link constraint do not participate
in IK solutions.
Link to Wor ld
You can also link an object to the world using the
Link to World button. This will keep the object
stationar y without the use of a dummy object. Just
clickLinktoWorldandtheworldisautomatically
entered as a Target.
Key Modes
You can choose between three different key modes,
which determine how keyframes are written on
the linked objects as part of the link constraint.
These options provide the following:
No Key Mode—No keys are created any of the
objects involved. No keys will be visible in the
track bar.
Key Nodes—Sets keys for some of the objects.
Child applies keys to the child object only. Pa r e nts
applies keys to both parents and the child object.
K ey Entire Hierarchy—This applies key frames to
the chosen nodes and t heir entire hierarchies.
Child keys the chosen object and the nodes in
its hierarchy up to the world. Pa r e nt s keys both
parents and the child and all three hierarchies up
to the world.
Side Ef fects of the Link Constrai nt
The Link constraint works to keep a child object
from jumping position at the time when the link
changes from one parent to another parent.
Considering the previous example, the following
should hold true:
• During f rames 0 to 50 the ball remains constant
relative to the first hand.
• During frames 50 to 100 the ball remains
constant relativ e to the second hand.
• At frame 50, the time when link control
changes, the ball does not jump.