an item using the Hypergraph

Viewing hierarchies using the Hypergraph

In the following steps, you use the Hypergraph to view the hierarchy for the mechanical arm. The

Hypergraph is a scene management editor that presents a graphical view of the scene hierarchy. It allows

you to more easily create, understand, and manage the hierarchy of objects and nodes in your scene.

To view hierarchies using the Hypergraph

1. From the perspective view's panel menu, select Panel > Layouts > Two Panes Stacked.

The workspace displays two panels stacked on top of each other with an identical perspective

view of the scene.

2. In the lower panel, select Panel > Panel > Hypergraph.

The lower panel displays the Hypergraph.

3. In the Hypergraph menu, select Graph > Scene Hierarchy.

If the menu item appears dimmed, it indicates that the Hypergraph is already displaying the scene

hierarchy

The Hypergraph displays with a black background by default. In order to see the relationships

between the items, the background has been modified for the images in this lesson.

4. In the Hypergraph menu, select View > Frame All to see all the components of your scene.

The boxes represent the nodes for the various items in the scene. Some items in the scene have already

been parented into a hierarchy. This is indicated by the lines connecting some of the nodes. Selecting

the nodes in the Hypergraph also selects the item in the scene view.

To select an item using the Hypergraph

 In the Hypergraph, click each of the separate items in the hierarchy at the parent level to select

them. At the same time, observe which objects become highlighted on the model in the

perspective view.

Hierarchies combine the various objects into discrete components for the mechanical arm, that is, the

base, lower arm, middle arm, upper arm, etc. If you select and rotate any of the parent nodes in the

hierarchies, none of the other arm components follow because they are not combined into one unified

hierarchy.

 Creating a skeleton hierarchy

To link the various components of the mechanical arm into a hierarchy that can be posed, you need to
create a skeleton. A skeleton is a hierarchy of joints that are connected together with bones.
In the scene, a joint represents a special type of node that gets created in a skeleton hierarchy. A joint
acts as the parent node for any other joints that occur in the hierarchy below it. Each joint has a
rotational pivot point associated with it. A bone is the visual representation used in the scene view to
connect the joints and help visualize the joint chain.

A skeleton is similar to a skeleton in the real world in that it acts as the underlying structure for the
surfaces to be attached. While you can view the skeleton with its bones and joints in the scene view, it
does not appear in your rendered images. Its purpose is to assist you in setting up and posing your
models and characters and to visualize the motion you want to achieve.

Skeletons are integral to the animation of any character or hierarchical model. Examples of characters
that use skeletons are two and four legged animals. Skeletons are also useful for animating other organic
components such as the tail of an animal, a tentacle of an octopus, or a snake.

In the following steps, you create a simple skeleton consisting of four joints that you combine with the
mechanical arm model into a skeleton hierarchy, allowing you to pose and animate the model.

To create a skeleton for the mechanical arm

1. In the perspective view menu, select Panels > Orthographic > side.
The view updates to display the side view.

You need to view the components of the mechanical arm fully in the side view so you can draw
the joints for the skeleton.

2. Resize the side view to a larger size by dragging the border between the side and Hypergraph
panel views downwards.

3. In the side view menu, select Shading > Wireframe (Hotkey 4).

.

4. From the main menu, select Skeleton > Joint Tool > .
The Tool Settings window for the Joint Tool appears. The Joint Tool is used to create the joints
and bones for a skeleton.

5. In the Joint Tool settings window, do the following:

o Click Reset Tool to set the tool to its default settings.

o Hide the Tool Settings window by clicking the right-pointing arrow that is located in the upper
left corner of the Tool Settings window.

 In the side view, starting from the base of the mechanical arm, do the following:

o Click in the center of each pivot pin on the mechanical arm to place four joints as shown in the
image below.

Try to click as close to the center of each pivot pin as you can, as the rotation of the joints on
the model will be based on the location of the joints on the skeleton. As you place the joints, a
bone appears, connecting each joint. (Because the model lies along the YZ plane, the joints are
created close to the center of each corresponding joint on the mechanical arm model.)

o After you place the fourth joint, press Enter to indicate that the last joint has been placed.

7. In the Hypergraph, dolly the view to see the skeleton node hierarchy you just created. (It appears
at the right side of the view.)

8. In the Hypergraph, select the joint1 node.

The entire skeleton becomes selected. Any rotations on this node also affect anything lower down
the hierarchy.

9. Select joint2 (You can also press the down arrow on your keyboard to select further down the
hierarchy).




The skeleton is selected from joint2 downwards in the hierarchy. Any rotations that you make on
this node affect only joint2 and nodes below joint2.

Once a skeletal hierarchy is created, the various surface components can be added to the hierarchy.