Linking and Unlinking Objects

The general process of creating links is to build the hierarchy from child to parent. You click Select and Link on the toolbar, select one or more objects as children, and then drag the link cursor from the selection to a single parent object. The selected objects become children of the parent object.

Once objects are linked, any transformations applied to the parent are also applied to its children. For example, if you scale the parent to 150%, the size of its children and the distance between the children and the parent are also scaled by 150%.

Click Unlink Selection to remove the link from selected objects to their parents. Any children of the selected object are unaffected.

You can quickly unlink an entire hierarchy by double-clicking the root object to select the object and all of its children. Then click Unlink Selection.

You should establish links before you begin animating objects. This linkage of objects cannot be animated, and these links exist throughout an entire animation. See Animating Hierarchies. If you do want to animate a linkage use the Link constraint. This lets you link to different objects at different frames.

A complex mesh hierarchy can be displayed with the links visible, or even with the links replacing the mesh objects. Select the objects and then on the Display panel, open Link Display, then turn on Display Links to see the links and Link Replaces Object to see only the links and not the objects.

The way the children behave toward one another is governed by the inheritance of the transforms down the chain. Setting joint limits on individual child objects can influence this inheritance. If three children in a row all have their rotational axes made inactive, they will not be able to rotate, and so a piece of the chain will appear stiff. Or if only one axis is made active as a sliding joint, the component can separate in space from the chain.

Any hierarchy of object or bone systems can have its joint limits defined. Select all the objects, and turn on their bone display. Select the bone and open the hierarchy panel > IK tab. Scroll down to the Sliding and Rotational Joints. There, you can activate axes and set their individual limits.

Note: Different IK solvers use different joint limits. When using a bone system, add the IK solvers first, then set the joint limits second.