The basic concept behind Motion Tracking and Stabilization is to follow an object as it moves around from frame to frame in a piece of footage. Once you understand how it works, you can:
•Stabilize the footage: If you know this object was supposed to be in the same place from frame to frame, but it moves for some reason, After Effects can track the object's movements, then animate it to move on the exactly the opposite direction so it appears to be steady. Check out my tutorial on Basic Stabilization for more information.
•Make one object follow another: If you know how an object is moving through a scene, you can then make another object of your choosing follow the exact same path.
To do this, you need to show After Effects a “feature region” in the footage for it to track. The best features have clearly defined, consistent shapes with distinct edges. They also have contrasting color or brightness compared with the pixels around them. After Effects has the ability to adapt what it is looking for from frame to frame, but the less the feature changes size or shape the better.
Basic Motion Tracking in After Effects CS3
In this tutorial, I have a slow zoom out and pan of a sailboat going from the right edge to the left edge. In this tutorial, we want to create text and have it track and follow the boat. We will use a Null object to track the boat.
1. Lets start off by creating new text and a new solid by going to the Layer Menu. Resize the solid to act as a “pointer” for the text.
2. In our composition we now have the video clip, text, and a solid. Now we're ready to get started. To make sure we're at the beginning of our timeline, press the Home key.
3. Select the video clip layer, then click Track Motion in the Tracker Controls Panel. This will open the clip in its own Layer panel and create a tracking point. Click inside the track point somewhere that you see the black cursor with the four-arrow tail, and drag the track point until it is centered at the point of interest (the boat's tip in this tutorial.) Resize the track point if necessary.
4. Click on the Options button in the Tracker Controls and position the Motion Tracker Options dialog where you can still see your point of interest. The Channel setting is the first option. Determine what sort of contrast there is between the point of interest and the surrounding background. In this case, I'm going to choose Luminance. The Adapt Feature settings are next. This tip of the boat does not change that much in the scene so I will leave Adapt Feature on Every Frame off. Set the popup to Stop Tracking so it will be obvious if After Effects can't follow this feature any longer. Then click OK.
5. Decide which layer will receive your motion track.
6. Select Layer>New>null Object; it will appear in the Timeline panel.
7. In the Tracker Controls, click on Edit Target and select your Null. Click Ok and verify that the name of the appears next to Motion Target. Click on Apply and click OK in the Motion Tracker Apply Options dialog that appears. The Comp panel will come forward with your null object selected showing its new motion path.
8. Select the text layer, then Shift+click the solid “pointer” layer and drag them into the desired position in relation to the boat's tip.
9. Press Shift+F4 to reveal the Parent panel if it's not already visible. With the two layers still selected, click on the Parent popup for either one of them and choose your null.
10. Ram preview and watch the text follow the boat!
Corey Richards's Background
With a background as a video editor, videographer, 3d modeler/animator, web designer, and graphic artist, Corey is about as diverse as they come. As the Director of Web Services for the DVPA, Corey ensures that the DVPA community stays well informed of the surrounding news and changes in the industry.