Graphics Programs Reference
In-Depth Information
If you get strange results when you connect the rotations of objects (for example, if the
wheels flip over or rotate the opposite direction of the control wheel), try disconnecting all
the connections, freezing transforms, and reconnecting the attributes.
Controlling the Wheel Arms
You've now automated the animation of the wheels. Next, you'll figure out how to connect
the wheel arms to the wheels and drive their motion as well. To do so, follow these steps:
1. Create a single joint that lines up with the first wheel arm. The root joint is placed
where the wheel arm meets the middle wheel (control wheel), and the end joint
is placed where the wheel arm meets the pump arm, as shown in Figure 9.66. The
pump arm has been templated in this graphic (displays in light gray wireframe) to
show you the entire wheel arm and joint.
Figure 9.66
Create a joint from
the middle wheel to
the pump arm at the
first wheel.
2. Group the joint under the control wheel's node, as shown in the Outliner in Figure 9.67.
Then, group the wheel arm under the top joint. This way, the joint rotates with the con-
trol wheel, also shown in Figure 9.67, albeit incorrectly for the pump arm.
3. As you saw in Figure 9.67, the joint isn't rotating properly to make the pump arm work
right. The other end of it needs to attach to the pump arm in front of the front wheel,
not f fly up in space. You can use an IK handle for this. Make sure the rotation of the
control wheel and the joint/wheel arm are set back to 0 to place them in the original
position. In the Animation menu, choose Skeleton
➔
IK Handle Tool. Make sure the
settings are reset for the tool. Select the root joint as the start joint for the IK Handle.
Select the other tip of the bone as the end effector. You now have an IK handle at the
tip where the wheel arm connects to the pump arm, as shown in Figure 9.68.
