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Smoothing Motion with Roving Keyframes

Frequently, adjusting a motion path causes drastic and unwanted fluctuations in timing. The layer goes where you want in terms of space, but its movement lags and lurches from one keyframe to the next. In the speed graph, these abrupt changes look like steep hills and chasms. You can try to adjust the speed and timing of the problem keyframes manually, or you can convert them into roving keyframes.

Roving keyframes retain their values; but their position in time is adjusted automatically so that the property’s speed becomes consistent, and the property’s speed graph flattens out. The adjustments are derived from the values of the standard, time-bound keyframes before and after the roving keyframes. Moving the first or last keyframe automatically readjusts the roving keyframes in between. This way, you can change the duration of the animation without having to carefully adjust the speed between each part.

If you don’t want a keyframe to rove, you can convert it back to a standard keyframe, which is locked to time.

To smooth motion with roving keyframes:

  1. Reveal a property’s speed graph in the Graph Editor.
  2. Select a range of keyframes other than the first or last keyframe for the property (Figure 9.81).
  3. The keyframes preceding and after the range must be locked to time. That is, they must be standard, nonroving keyframes.

    Figure 9.81 Select a range of keyframes between two keyframes. This uneven speed graph indicates sudden changes in speed between keyframed positions.

  4. In the Graph Editor, click the Edit Keyframe button, and then choose Rove Across Time from the pop-up menu (Figure 9.82).
  5. The selected keyframes become roving key*frames, moving in time so that the speed is constant (as evidenced by the speed graph). The roving keyframe icons appear as small dots (Figure 9.83).

    Figure 9.82 Selecting Rove Across Time in the Graph Editor’s Edit Keyframe pop-up menu...

    Figure 9.83 ...converts the selected keyframes to roving keyframes, which shift in time to create constant speed between the standard keyframes. Contrast this speed graph with the one in Figure 9.76.

To convert a roving keyframe to a standard keyframe:

  1. Reveal a property’s speed graph in the Graph Editor, and select one or more of its roving keyframes (Figure 9.84).
  2. Figure 9.84 Reveal the speed graph of a property, and select one or more of its roving keyframes...

  3. Click the Graph Editor’s Edit Keyframe button, and deselect Rove Across Time in the pop-up menu (Figure 9.85).
  4. The keyframe is converted from a roving keyframe to a standard keyframe that is locked to time. Its keyframe icon changes from a small dot to its standard icon (a small box in the Graph Editor, or a diamond icon in the standard view of the time ruler).

    Figure 9.85 ...and deselect Rove Across Time to convert the selection to standard keyframes, which are locked to time.

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