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### Animating a Bat with Bones

Timing and movement are so important to animation that they’re something you’ll always perfect. Keep your eyes open. Motion information that you can use in your animations is all around you. Suppose, for example, that you want to animate a human walk cycle. You can get relative information just by watching your coworker move across the room. Other motions are often hard to reference, however, such as motions of animals or birds.

Exercise 12.7 Flapping Bat Wings with Bones

In this exercise, you’re going to rotate the bones of a bat to make the wings flat. A slight offset on the outer bones will provide for a less rigid movement. You also will move the bones in the body so that more than just the wings are moving. The scene you’ll use is a bat with bones already in place, which were created with Skelegons. It also has weights set on the arms for added control.

1.
Load the BatBoneKeyMe scene from the accompanying CD. Select Bone02(3). Press y to rotate. Note the rotational position for the Pitch—it’s at –45 degrees. This is your first frame. You’ll want the last frame to be at this exact position as well so that the wing can loop. So, with the bone in this position, create a keyframe at 15. Now rotate the bone on its pitch about 43 degrees (downward). Create a keyframe at frame 7.

2.
Press the down arrow to select the next bone, Bone03(2). Its keyframe at 0 shows the bone rotated at –55.0 degrees on the Pitch. Create a keyframe for this bone’s position at 15. Rotate it downward to 30.0 degrees and create a keyframe at frame 7. Also create a keyframe in this same position at frame 9.

This bone will lag behind the first bone, creating a slight extra motion so that the wing sort of sweeps down, instead of just rotating.

3.
Select the next Bone04(2) and note its initial position at frame 0 to 45 degrees. Create a keyframe for it at this position for frame 15. Rotate it on the Pitch to –37.00 and create a keyframe at 7. Then rotate it to 70.00 and create a keyframe at 9. Figure 12.48 shows the first wing in position.

##### Figure 12.48. The bat’s right wing is put into motion after movement of just a few bones.

4.
With the same bone selected (Bone04(2)), open the Graph Editor. Select the Position P (pitch) channel, and set the Post Behavior to Repeat. Do the same for the other two bones in the wing.

5.
You can set the exact motions for the bones on the bat’s left wing, making sure to set the Post Behavior to Repeat as well. When you keyframe the bones on the left side of the bat, however, offset the timing by a frame or two. Also don’t use the exact rotations for the bones—vary them a bit for added realism.

6.
Select the bat’s body bone, Bone01(1). At frame 0, you’ll see the Pitch is set to –3.03. Create a keyframe for this position at frame 15. Then rotate it to 5.0 degrees on the pitch and create a keyframe at 6. Also repeat its Post Behavior in the Graph Editor.

Drag through the timeline and you’ll see the bat flapping its wings, while its body is slightly moving.

From this point, use the same formula to animate other bones of the bat, such as the feet, neck, and head. If the wings swoop downward, the neck and head would raise up a bit, and vice versa. Here are a few things to remember:

• Make sure the first and last frames are the same for looping motions.

• Add secondary motion to the object’s body.

• Don’t forget to animate the feet and/or legs as well.

• When rotating the bones in the wing, add a slight offset by adding extra keyframes for child bones so that the wings are fluid and not as stiff.

This technique is very useful for bats, birds, and even dragons.

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