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Filed under: Motion Graphics •Post Production •Visual Effects •

A Track of the Clones

Making tracks

The Motion Tracker and Stabilizer were completely overhauled in After Effects 6.0 at the same time the Paint Tools were introduced; although the look of their options have changed in subsequent versions, the Tracker still works pretty much the same. One of the nicer features introduced to the Tracker in version 6 was that no longer have to apply a track as soon as your create it – you can make as many tracks as you want, and use them later as your needs (or desired workflow) dictates. There is no need to manually save tracks, as they are now automatically stored as keyframe data for the layer.

To set up a track, switch back to the Selection Tool (shortcut = V), and open Window > Tracker Controls (seen at right). Click on Track Motion; the familiar Tracking Region boxes will appear in the Layer window. Move and resize the inner Feature Region box to encompass the plane, and the outer Search Region to encompass how much the plane might move from frame to frame. The Track Point crosshair should be centered over the plane – this is where the Clone stroke will end up. It is still important to at least verify the options for the tracker, but fortunately the defaults from version 6.0 forward are much better, and happen to work fine for this particular track.

Expressive clones

To finish off our repair, we need to have the Clone stroke’s Clone Position (the “from” point) and Position (the “to” point) use the track data we just created. You can copy and paste keyframes; in our case, we’ll take advantage of expressions. (Commotion and combustion have their own ways to assign track data to paint strokes.)

If you don’t already have the Clone parameters twirled open in the Timeline panel, type PP, and twirl open its Stroke Options and Transform parameters. Then type Shift+U to also reveal the keyframes created by the Motion Tracker. This is lot of parameters for the Timeline window to display; to reduce the clutter, you can employ another feature introduced back in After Effects 6.0: Solo Selected. Click on the Track Point > Attach Point parameter, then Command+click (Control+click) on Stroke Options > Clone Position, Stroke Options > Clone Time Shift, and Transform > Position to select them as well. Type SS (two S’s in quick succession), and only the selected parameters will remain in the Timeline window. Don’t confuse the stroke’s Position parameter with the layer’s overall Position! Pay attention to how far the parameter’s name is indented; make sure it is inset from the Clone stroke’s name.

Time to make the stroke follow the track. Option+click (Alt+click) on the animation stopwatch for Clone Position to enable Expressions for this parameter. Then drag the pick whip tool that appears for this parameter up to the words Attach Point, and hit Enter – Clone Position will now be expressed to follow the Attach Point. Then do the exact same for the stroke’s Position. RAM Preview, and the plane should now be cloned out.

The Timeline window of our finished project (this screen capture is from version 6; the information is the same through CS3). The Clone stroke’s Clone Position and new Position are expressed to follow the Attach Point keyframes created by the motion tracker.

If you can still see pieces of the plane, you may need to increase the stroke’s Diameter. If pieces of something else in the scene – such as the main plane – come too close to the cloned-out plane and momentarily appear in the sky, you may need to change the time you cloned from. You can keyframe the Clone Time Shift parameter same as any other; for example, you might need to move from two seconds earlier to two seconds later in time. Using Hold keyframes will ensure you don’t accidentally interpolate through “zero time” where you will just be cloning the original plane back on top of itself.

If that seems like a lot of steps, we can honestly tell you it takes less time to actually do than to read about it! The hidden story in all of this is: When possible, let the tool do the work for you. You’ll save valuable brain cells and hair, plus get more sleep as well.

The content contained in our books, videos, blogs, and articles for other sites are all copyright Crish Design, except where otherwise attributed.

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