Graphics Programs Reference
In-Depth Information
4. Move ahead in the animation about three frames to frame 15. Scale the ball up in the
Y
-axis slightly past normal to stretch it up (about 1.15) immediately after its bounce,
as shown in the image on the right in Figure 8.12. Three frames later, at frame 18, set
the
Y
-axis scale back to 1 to return the ball to its regular shape
5. Scrub your animation, and you should see the ball begin stretching even before it
hits the ground. That's a bit too much exaggeration, so open the Graph Editor and
move the
Y
-axis scale key from 9 to 11. Now, the ball squashes when it hits the f floor
and stretches as it bounces up.
6. Repeat this procedure for the remaining bounces, squashing the ball as it hits the
f floor and stretching it as it bounces up. Remember to decay the scale factor as the
ball's bouncing decays to a stop, as when you decayed the height of the ball's bounce
earlier. The final bounce or two should have very little squash and stretch, if any.
Load the file
ball_v03.mb
from the Bouncing_Ball project on the CD to get to this
point. And now, let's rotate the ball as it bounces.
Rotation
Let's add some roll to the ball in these steps:
1. Select the ball's rotate node, and select Modify
➔
Center Pivot to set that node's pivot
at the center of the ball.
2. At frame 1, press Shift+E to set keys for rotation at (0,0,0).
3. Scrub to the end of your animation (frame 100 in this example), and set a value of
-480 for Rotate Z in the Channel Box, as shown in Figure 8.13.
4. Open the Graph Editor to see the rotation curve on the ball's rotate node. It's a linear
(straight) line angled down from 0 to -480. You need the rotation to slow to a stop at
the end of the animation, so select the final keyframe and click (
) to make it a f lat
tangent.
Figure 8.13
Setting a roll
for the ball
