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Lesson 2. Ballet Special Bumper > Setting roving keyframes

Setting roving keyframes

One way to smooth out the speed of the layer is to set roving keyframes. Creating roving keyframes separates the x, y (or spatial) coordinates of the Position keyframes from their specific points in time.

  1. Make sure the T layer is selected, and then zoom in the Time Layout window.

  2. To create roving keyframes, deselect the tiny check boxes below the four middle keyframes. The first and last keyframes in a layer cannot rove, so they don't have check boxes.


    Figure .


    As you deselect the check boxes, the Speed graph becomes more and more flat, which indicates a constant rate of speed. Notice also that the dots in the motion path in the Composition window have become more evenly spread out.

    The keyframe icons change to small circles and shift a bit, disconnecting from their original points in time.


    Figure .


  3. Click the triangle next to the T layer to collapse the layer outline.

  4. Select the E layer, and then click the triangle next to Position to display the Speed graph. This time leave the first check box selected, and then deselect the last four check boxes to create roving keyframes. The keyframe at 08:00 remains non-roving so that the motion starts at a specific point in time.


    Figure .


  5. Select the lower L layer, and then click the triangle next to the Position property. Leave the first roving keyframe navigator check box checked, and then deselect the last four check boxes to create roving keyframes.

  6. Repeat step 5 for each of the remaining layers for the word ballet.

    Because using roving keyframes separates the spatial position coordinates from a specific point on the timeline, you would not use roving keyframes if you wanted to synchronize an animation event, such as Position, with a specific point in time, such as a key point in music.

    In this exercise, however, the desired effect is to have all of the letters follow one another along a motion path while remaining evenly spaced along that path. To achieve this effect they must hit certain spatial points (position coordinates) along the path at a constant rate of motion. Because the letters have varying distances to travel from their original starting points to reach the end of the motion path, locking them to specific points in time will cause the letters with greater distances to move faster as they travel between keyframes. Those with shorter distances will move more slowly, creeping along, causing the letters to pile up on top of each other, and the type will become unreadable to the viewer.

    Setting a Roving keyframe unlinks the position keyframe from its specified point in time. The first and last keyframes are now temporal beginning and end points, and an even rate of motion is applied as the letter travels between those end points. The letter still hits the same spatial points on the path, but no longer at the original times specified. In short, we know when we want a letter to begin moving from it's starting position (first keyframe), when we want it off screen (last keyframe), and the path that we want it to travel along (original position keyframes). We don't really care, however, when it hits those mid-points along the path as long as the letters all travel at the same constant rate of speed, remaining evenly spaced and readable.

  7. Take a look at motion of the letters using RAM Preview: press the 0 key on your numeric keypad.

  8. When you are finished previewing, collapse all the layer outlines, and then save the project.

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