Adjusting Hierarchies


When skeletons become complex, you need to work with the joint hierarchies as they are, instead of taking them apart and putting them back together again and again. Maya provide a number of useful tools to help you work within a complicated skeleton. These tools let you mirror, move, insert, and delete joints inside the existing hierarchy.

To save time, once you create a leg or an arm, you can mirror the joint, which makes a duplicate leg or arm appear on the other side of the body.

To mirror joints:

1.

Using the leg from the "To parent joints" task, select the hip joint (Figure 10.11).

Figure 10.11. The hip joint is selected so that the leg can be mirrored over to the other side.


2.

From the Skeleton menu, select the box next to Mirror Joint.

The Mirror Joint Options dialog box opens.

3.

For Mirror Across, select YZ (Figure 10.12).

Figure 10.12. The YZ option is chosen so that the leg will mirror across the YZ plane.


4.

Click Mirror.

A new leg appears on the other side (Figure 10.13).

Figure 10.13. The opposite leg is created using the Mirror Joint Options dialog box from the Skeleton menu.


Tips

  • If the leg was built in the Side view, you should mirror it across the yz plane. To figure out which plane you should use, look at the View axis in the corner of the panel and imagine two of the axes forming a plane that you want to mirror across. If the new leg doesn't appear in the correct location, undo the mirror joint and try choosing a different plane to mirror across in the Mirror Joint Options dialog box.

  • Don't mirror a joint that falls on the center line of the body: If you do, you'll end up with two joints on top of each other.

    When you move a joint to position it, all the joints beneath it in the hierarchy move along with it. You can move a joint independently of its position in the hierarchy by using pivot move mode.


To move a joint:

1.

Start with your skeleton from the previous task.

2.

Select the knee joint (Figure 10.14).

Figure 10.14. The knee joint of the leg has been selected so that it can be moved.


3.

Press .

4.

Move the knee backward.

The rest of the leg moves with it (Figure 10.15).

Figure 10.15. As the knee is moved back, the foot bones move with it. Note that the bone between the hip and the knee becomes longer.


5.

Press to undo the last move.

6.

Press on the keyboard.

You're now in pivot move mode.

7.

Move the knee backward.

The rest of the leg doesn't move with it (Figure 10.16).

Figure 10.16. When the knee joint is moved in pivot move mode, the foot, which is below it in the hierarchy, stays put.


8.

Press to undo the last move. Press again to get out of pivot move mode.

Inserting and deleting joints

Sometimes you need to insert a new joint into your skeleton after you've laid it out. Rather than unparenting, adding a new joint, and then re-parenting, use the Insert Joint tool. This handy tool keeps your existing skeleton intact by splitting your bone and inserting a new joint in your hierarchy.

Conversely, you may find that you've created more joints than you need. If so, you can select the joint and remove it from the hierarchy without deleting any additional nodes, like deleting the joint would do.

To insert a joint:

1.

Create a skeleton of several joints (Figure 10.17).

Figure 10.17. A skeleton of several joints is created in an orthographic view.


2.

Choose Skeleton > Insert Joint Tool.

3.

Click a joint, and drag out the new joint.

The new joint is inserted between the joint you clicked and the joint beneath it in the hierarchy. It's easiest to do this in an orthographic view (Figure 10.18).

Figure 10.18. A new joint is created between two existing joints. It's positioned between the joints both physically and in the hierarchy.


4.

Press to finish, and exit the tool.

To remove a joint from the hierarchy:

1.

Click the joint you would like to remove (Figure 10.19).

Figure 10.19. You can select a joint by clicking it in the modeling window or by clicking the corresponding joint node in the Hypergraph.


2.

Choose Skeleton > Remove Joint (Figure 10.20).

Figure 10.20. Select Skeleton > Remove Joint.


The joint is removed from the hierarchy and deleted from the scene. Now that the selected joint has been removed, the bone from its parent ends at the selected joint's child (Figure 10.21).

Figure 10.21. The selected joint (joint7) is completely deleted from the scene and can no longer be viewed in the Hypergraph.


Sometimes you'll want to disconnect a portion of a previously created skeleton to use it in a new character. For instance, you may want to create a half-human character that uses a human joint systemwith human-like arms but nonhuman-like legs. By disconnecting the center joint, you can use the upper half of the human skeleton on the human half of the new character.

To disconnect a joint from the hierarchy:

1.

Click the joint you would like to disconnect from the hierarchy (Figure 10.22).

Figure 10.22. You can select a joint by clicking it in the modeling window or by clicking the corresponding joint node in the Hypergraph.


2.

Choose Skeleton > Disconnect Joint (Figure 10.23).

Figure 10.23. Select Skeleton > Disconnect Joint.


The selected joint and its children are disconnected from the original hierarchy.

3.

Choose Window > Hypergraph.

The Hypergraph opens in a new window.

4.

Press to focus all the joints in the Hypergraph window.

The skeleton is split into two hierarchies that can be selected and moved independently of each other (Figure 10.24).

Figure 10.24. Although in the Modeling view the skeleton still appears to be one, you can see in the Hypergraph that there are now two separate hierarchies.


Tip

  • Disconnecting a joint is different from unparenting it. Disconnecting leaves a new joint where the base of the disconnected hierarchy was removed, whereas unparenting removes the joint (Figure 10.25).

    Figure 10.25. On the left is the original skeleton. In the middle, the Disconnect tool has been used and the piece has been moved away slightly. On the right, the joints have become unparented, and a bone is missing.





Maya 7 for Windows and Macintosh(c) Visual Quickstart Guide
Maya 7 for Windows & Macintosh
ISBN: 0321348990
EAN: 2147483647
Year: 2006
Pages: 185

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