3ds Max 2012 Bible - Kelly L. Murdock [258]
Setting parameters
The Parameters button on the Motion panel lets you assign controllers and create and delete keys. Controllers are custom key-creating algorithms that can be defined through the Parameters rollout, shown in Figure 21.7. You assign these controllers by selecting the position, rotation, or scaling track and clicking the Assign Controller button to open a list of applicable controllers that you can select.
FIGURE 21.7
The Parameters section of the Motion panel lets you assign controllers and create keys.
Cross-Reference
For more information on controllers, see Chapter 22, “Animating with Constraints and Simple Controllers.” •
When a keyable object is selected, below the Assign Controller rollout is the PRS Parameters rollout where you can create and delete Position, Rotation, and Scale keys. You can use this rollout to create Position, Rotation, and Scale keys whether or not the Auto Key or Set Key buttons are enabled. Additional rollouts may be available, depending upon the selected controller.
Below the PRS Parameters rollout are two Key Info rollouts: Basic and Advanced. These rollouts include the same key-specific information that you can access using the right-click pop-up menu found in the Track Bar.
Using trajectories
A trajectory is the actual path that the animation follows. When you click the Trajectories button in the Motion panel, the animation trajectory is shown as a spline with each key displayed as a node and each frame shown as a white dot. You can then edit the trajectory and its nodes by clicking the Sub-Object button at the top of the Motion panel, shown in Figure 21.8. The only subobject available is Keys. With the Sub-Object button enabled, you can use the transform buttons to move and reposition the trajectory nodes. You can also add and delete keys with the Add Key and Delete Key buttons.
FIGURE 21.8
The Trajectories rollout in the Motion panel enables you to see the animation path as a spline.
For more control over the trajectory path, you can convert the trajectory path to a normal editable spline with the Convert To button. You can also convert an existing spline into a trajectory with the Convert From button.
To use the Convert From button, select an object, click the Convert From button, and then click a spline path in the scene. This creates a new trajectory path for the selected object. The first key of this path is placed at the spline's first vertex, and the final key is placed as the spline's final vertex position. Additional keys are spaced out along the spline based on the spline's curvature as determined by the Samples value listed in the Sample Range group. All these new keys are roughly spaced between the Start and End times, but smaller Bézier handles result in more closely packed keys.
Click the Collapse button at the bottom of the Trajectories rollout to reduce all transform keys into a single editable path. You can select which transformations to collapse, including Position, Rotation, and Scale, using the options under the Collapse button. For example, an object with several Controllers assigned can be collapsed, thereby reducing the complexity of all the keys.
Note
If you collapse all keys, you cannot alter their parameters via the controller rollouts. •
The Views menu includes an option to Show Key Times. The Show Key Times command displays frame numbers along the trajectory path where every animation key is located. Enabling this option displays the frame numbers next to any key along a trajectory path. You can make the trajectory visible for any object by enabling the Trajectory option in the Object Properties dialog box.
Tutorial: Making an airplane follow a looping path
Airplanes that perform aerobatic stunts often follow paths that are smooth. You can see this clearly when watching a sky writer. In