9

Locking Object Transforms 433
2. Select the sphere and click Reset XForm. The
sphere remains the same size but its child
reverts to its original size and position. Here’s
what has happened:
The 200% scale has b een placed in an XForm
modifier on the sphere’s modifier st ack . The
sphere has a true radius of 40 units, Creation
Parameters report a radius of 20 units, and
absolute local scale is 100%.
The sphere’s child object now sees only the
100% loca l scale so it reverts to its original size
and pos ition.
Locking Obj ect Tr a nsfor ms
You can lock an object’s ability to move, rotate, or
scale about any of its local axes by select ing objects
and then setting options on the Locks (page 2–500)
rollout of the Hierarchy panel.
Enabling and disabling L ocal transform axes is
also refer red to as setting degrees of freedom
(DoF)foranobject.Ifanaxisisenabled,anobject
is free to transform about that Local axis.
The Locks rollout contains three groups: one each
for Mov e, Rotate, and Scale. Each group con tains
three options, one each for the X, Y, and Z Loca l
axes of the selected objects.
• When turned on, the objects cannot be
transformed about the selected Local axes when
you directly use one of the transform tools.
Objects can still be transformed by other means
such as being a child of a transformed p arent
object or being part of an inverse kinematics
chain.
• When tu rned off, objects can be freely
transformed about the unlocked Local axes.
Animating Attachment
You assign an Attachment constraint (page 2–393)
to cause an object to hold a position on the surface
of another object. The Attachment constraint
is not a hiera rchical link, but it has the effect of
"linking" an object to the surface of another object
as follows:
• Attach a "source" object to the face of a "target"
object so that the s ource object acts as if it’s
gluedtothetargetobject,nomatterhowthe
surface of the target object is deformed.
• Animate the Attachment par ameters so that
the source object moves over the surface of the
target object.
Unlike hierarchical linking, which considers only
object transforms, an object using an Attachment
constraint follows the deformations of another
object based on that object’s modifiers and space
warp bindings.
See Animation Constraints. (page 2–392)
Setting Attachment Parameters
You use features on the Attachment Parameters
rollout on the Motion panel, to pick a target object
and position the source object.
• Click Pick Object, then click the target object to
perform the attachment.
• Click Set Position and click or drag on the
surface of the target object to place the source
object onto the surface.
If you want to move the source object along
the normal of the face (move it below or
above the face) click Affect Object Only on the
Hierarchy p anel and move the object, u sing
Local t ransform coordinates.
• TurnonAligntoSurfaceifyouwanttoalign
the world Z axis of the source object with the
surface normal of the target object. Even with