One of the most useful tools in producing computer animation is the ability to link objects together to form a chain. By linking one object to another, you create a parent-child relationship. Transforms applied to the parent are also transmitted to child objects. A chain is also referred to as a hierarchy.

Left: A disassembled robotic arm is linked into a hierarchy.

Right: The assembled robotic arm uses rotational joints.

You can find the commands to build and manipulate hierarchies in the following places in the interface:

Common Uses for Hierarchies

Parts of a Hierarchy

The relationship between objects linked together in a hierarchy is analogous to a family tree.


Object that controls one or more children. A parent object is often controlled by another superior parent object. In the following figure, objects 1 and 2 are parent objects.


Object controlled by its parent. A child object can also be a parent to other children. In the following figure, objects 2 and 3 (the support and hub) are children of object 1. Objects 5 (the seats) are children of object 4, the Ferris wheel.


Parent and all of the parent’s parents of a child object. In the following figure, objects 1 and 2 are ancestors of object 3.

The seats of the Ferris wheel are children of the wheel, which is in turn a child of the base and support objects, as shown in the following hierarchy.


Children and all of the children’s children of a parent object. In the figures, all the objects are descendants of object 1.


Collection of all parents and children linked together in a single structure.


Single parent object that is superior to all other objects in the hierarchy. All other objects are descendants of the root object. In the figures, Object 1 is the root.


All the descendants of a selected parent. In the figure below, the Rotational Hub, Ferris Wheel, and Seats represent the subtree under the Support object.

1. Root

2. Leaves

3. Subtree

Example of a hierarchical structure


Path through the hierarchy from a parent to a single descendant. In the figure above, the Support, Rotational Hub, and Ferris Wheel objects comprise a branch from the root to the leaf objects (the seats).


Child object that has no children. The lowest object in a branch. In the figure above, the Seat objects are leaf objects.


Connection between a parent and its child. A link transmits position, rotation, and scale information from parent to child.


Defines the local center and coordinate system for each object. You can think of a link as the connection between the pivot of a child object and the pivot of its parent.

  • Linking Strategy

    Before you begin linking any but the simplest hierarchy you should take a few minutes to plan your linking strategy. Your choices for the root of the hierarchy and how the branches grow out to the leaf objects will have important effects on the usability of your model.

  • Linking and Unlinking Objects

    Use Select and Link and Unlink Selection on the toolbar to make and remove links between objects.

  • Adjusting Pivots

    You can think of an object's pivot point as representing its local center and local coordinate system.

  • Viewing and Selecting Hierarchies

    There are a number of ways to view a hierarchy structure and select objects in it.