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434 Chapter 12: Animation
Align to Surface selected, you can always rotate
thesourceobjecttoorientitthewayyouwant
in relation to the t arget object.
If you were to align trees on an uneven terrain,
you would turn off Align to Surface so that all
of the trees g rew upright, regardless of the angle
of the terrain surface.
Animating Attachment Position
You can move to any frame and click Set Position
to animate the source object moving across the
surface of the target object. It is not necessary to
turn on the Auto Key button, because you are
working w ith an animation constraint.
When you set positions for the sour ce target on
multiple frames, its attachment to the target object
is only fixed at each key frame. Frames between
keys are interpolated and might not match the
target sur face. If you need the object to remain on
the target surface, try using a Surface Constraint,
rather than attachment.
Test your animation, and either adjust the values
of the keys, or add intermediate keys to better
match the target surface. Too many keys can result
in jittery movement of the source object, w hile too
few keys might result in the source object missing
thesurfaceofthetargetobjectoversomeframes.
Cha nging L ink I nher itance
Links can transmit transform information from
a parent to a child. By default, a child inherits all
of the tra nsforms of its pa rent. To set an objec t’s
ability to inherit the move, rotate, and scale
transforms of its parent, you use the Inherit (page
2–500) rollout of the Hierarchy panel. Use its
settings to limit which transforms a child inherits.
The Inherit rollout is available only when you have
selected a single object. When multiple objects are
selected, the rollout is disabled.
Setting Link Inher itance Options
Set the In herit options to release the link
comp onents b e tween a selected object and its
parent for any world axis of Move, Rotate, or Scale.
The options that appear when you expand the
Inherit rollout are determined by the transform
controllers assig ned to the selected object.
The Inherit rollout for objects using standard
position, rotation, and scale controllers contains
three groups: one each for Move, Rotate, and
Scale. Each group contains three options, one each
fortheX,Y,andZworldaxes.
• When turned on, transform information from
the parent is passed on to the child for the
selected World axes.
• When turned off, transform information for
the selected axes is ignored by the chi ld.
ImagineyouareanimatingaFerriswheelthat
rotates on t he world Y axis. The wheel is the parent
and the cars are its children. You want the cars to
ignore the Y axis rotation of the wheel. O therwise,
the passengers would all fall out. You use Link Info
to turn off the Y axis option on the Rotation group
of the Inherit rollout for each car.
Using the Li nk I nher ita nce U til it y
The Link Inheritance (page 2–435) utility works
exactly the same as the Inherit rollout in t he Lin k
Info group on the Hierarchy panel, except that you
can set link inher itance for multiple objects in a
selection set.
For example, on a Ferris wheel, you could select all
ofthecarsandusetheLinkInheritanceutilityto
turn off Y axis rotation for all the cars at once.