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2. With the squirt bottle object selected, choose the Modifiers⇒Animation⇒Skin Wrap menu command to apply the Skin Wrap modifier.

3. In the Parameters rollout, click the Add button and select the Box object. The Box object is added to the Skin Wrap list in the Parameters rollout.

4. Select the Box object and hide it in the scene.

5. Click the Play Animation button, and the hi-res bottle follows the same animation as the box object.

Figure 40.9 shows the squirt bottle as it moves through the scene.

FIGURE 40.9

Not all animated objects need a bone structure.

Using the Skin Morph modifier

Using the deformation options found in the Skin modifier, you can deform any part of the skin, but this feature relies on using gizmos found in an already complex envelope-editing mode. Skin Morph offers another way to deform a skin object using the underlying bones. The Skin Morph modifier is applied on top of a Skin modifier and lets you pick which bones to use in the deformation. For example, for bulging muscles, the forearm bone is rotated and should be added to the list in the Parameters rollout.

After selecting a bone from the Parameters rollout list, select the frame where the deformation is at a maximum. Then click the Create Morph button in the Local Properties rollout to create the morph target. Morph targets can be given names to make them easy to select later. The Edit button in the Local Properties rollout then lets you move the vertices for the deformation.

Tutorial: Bulging arm muscles

Perhaps the most common bulging deformation for characters is making the bicep muscle bulge as the forearm is raised. This effect can be simplified using the Skin Morph modifier.

To bulge an arm muscle using the Skin Morph modifier, follow these steps:

1. Open the Bulging bicep.max file from the Chap 40 directory on the CD.

This file includes a rough arm model with a Skin modifier applied attached to a four-bone chain.

2. With the arm skin selected, choose the Modifiers⇒Animation⇒Skin Morph menu command to apply the Skin Morph modifier on top of the Skin modifier.

3. In the Parameters rollout, click the Add Bone button and select the forearm bone object.

The bone object is added to the Skin Morph list in the Parameters rollout.

4. Select and rotate the forearm bone to the location where the deformation is at its maximum. Then select the bone object from the list in the Parameters rollout, and click the Create Morph button in the Local Properties rollout. In the Morph Name window name the morph Bulging bicep.

Tip

The forearm bone can be hard to see under the skin, but you can always select the bone using the Select by Name dialog box, which is opened by pressing H. •

5. In the Local Properties rollout, click the Edit button. This enables the Points subobject mode. Then enable the Edge Limit option in the Selection rollout, so the vertices on the forearm aren't accidentally selected. Drag over the points on the front of the bicep muscle in the Left viewport, and enable the Use Soft Selection option in the Selection rollout. Set the Radius value to 0.5, and scale the points to the right in the Left viewport to form a bulge. Click the Edit button again to exit Edit mode.

6. Select and rotate the forearm bone to see the bulging bicep muscle.

Figure 40.10 shows the arm muscle as it bulges along with the rotating forearm.

FIGURE 40.10

Using the Skin Morph, you can set a muscle to bulge as the forearm is rotated.

Using Character Animation Techniques

When it comes to character animation, several techniques can really help. Keeping these points in mind as you animate characters can make a difference:

• Use Biped: Manual rigging is useful for those cases where Biped won't work, but the tools and features found in Biped make it silly to look elsewhere for human characters.

• Use dynamics: Dynamic packages like reactor can provide incredibly realistic motion based on physical