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Figure 30-4: The Create Key dialog boxes enable you to create a Position, Rotation, or Scale key quickly.

If you right-click the spinner, a pop-up menu of options appears. Using this pop-up menu, you can Cut, Copy, Paste, and Delete the parameter value. You can also select Copy Animation, which copies all the keys associated with this parameter and lets you paste them to another parameter. Pasting the animation keys can be done as a Copy, an Instance, or a Wire. A Copy is independent; an Instance ties the animation keys to the original copy, so that they both are changed when either changes; and a Wire lets one parameter control some other parameter.

The right-click pop-up menu also includes commands to let you Edit a wired parameter, show the parameter in the Track View, or show the parameter in the Parameter Wire dialog box.

Using the Track Bar

The Max interface includes a simple way to work with keys: with the Track Bar, which is situated directly under the Time Slider. The Track Bar displays a rectangular marker for every key for the selected object. These markers are color-coded depending on the type of key. Position keys are red, rotation keys are green, scale keys are blue, and parameter keys are dark gray.

The current frame is also shown in the Track Bar as a light blue transparent rectangle, as shown in Figure 30-5. The icon at the left end of the Track Bar is the Show Curves button, which opens a mini Track View.

Keys

Figure 30-5: The Track Bar displays all keys for the selected object.

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Viewing and Editing Key Values

At the top of the marker’s right-click pop-up menu is a list of current keys for the selected object (or if there are too many keys for a marker, they are placed under the Key Properties menu). When you select one of these keys, a key information dialog box opens. This dialog box displays different controls depending on the type of key that is selected. Figure 30-6 shows the dialog box for the Position key. There are slight variations in this dialog box depending on the key type.

Figure 30-6: Key dialog boxes enable you to change the key parameters.

Note You can also access key-specific dialog boxes in the Motion panel for a selected object by clicking the Parameters button.

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Within each of these key dialog boxes is a Time value that shows the current frame. Next to the Time value are two arrows that enable you to move easily to the other keys in the scene. The dialog box also includes several text fields, where you can change the key parameters.

Most of the key dialog boxes also include flyout buttons for selecting Key Tangents. Key Tangents determine how the animation moves into and out of the key. For example, if the In Key Tangent is set to Slow and the Out Key Tangent is set to Fast, the object approaches the key position in a slow manner but accelerates as it leaves the key position. The arrow buttons on either side of the Key Tangent buttons can copy the current Key Tangent selection to the previous or next key.

The six different types of Tangents are detailed in Table 30-3.

Using the Motion Panel

You have yet another way to create keys: by using the Motion panel. The Motion panel in the Command Panel includes settings and controls for animating objects. At the top of the Motion panel are two buttons: Parameters and Trajectories.

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 30-7. These controllers are assigned 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.

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Below the Assign Controllers rollout is the PRS Parameters rollout, where you can create and delete Position, Rotation, and Scale keys. You can use this rollout to create 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 30-8. 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.

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 the selected object’s original position, and the second key is located at the spline’s first vertex position. Additional keys are added as determined by the Samples value listed in the Sample Range group. All these new keys are equally spaced between the Start and End times. The selected spline is traversed from its initial vertex around the spline in order to the last vertex.

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Figure 30-8: The Trajectories rollout in the Motion panel enables you to see the animation path as a spline.

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.

The Views menu includes an option to Show Key Times. Enabling this option causes the display of 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 this example, I’ve created a simple looping path using the Line spline primitive, and we use this path to make a plane complete a loop.

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To make an airplane follow a looping path, follow these steps:

Figure 30-9 shows the plane’s trajectory.

Figure 30-9: Using a spline path, the position keys are automatically set for this plane.