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After Effects CS4: Apprentice's Guide to Key Features is a series of guided tours with Chris and Trish Meyer. It is designed as a gentle introduction to some of the major features of After Effects CS4. This quick–start course is for beginners who already know how to animate, users who are not familiar with the latest version, or those who need to get up to speed with advanced tools. Chris and Trish cover features such as text animators, shape layers, expressions, and motion tracking. These guided tours are also included with the second edition of Chris and Trish Meyer's book, After Effects Apprentice (Focal Press).
To learn the basics of animating in After Effects CS4, check out After Effects CS4 Getting Started with Chad Perkins in the lynda.com Online Training Library®. To go deeper, see Chad's After Effects CS4 Essential Training. To get an overview of the new features in After Effects CS4, watch After Effects CS4 New Creative Techniques with Chris and Trish Meyer.
To purchase After Effects Apprentice—the book—go to www.amazon.com.
- Understanding 3D Axis Arrows and Camera Tools
- Working with Text Essentials and Animators
- Using Tracker controls
Skill Level Intermediate
If you want use the Motion Tracker and Stabilizer un After Effects, you need to do two things. One, get a good track point. Two, set good track options. The first thing you want to do is open up the Tracker panel. You can do that a couple of ways. You can up a Window > Tracker or you can change your workspace to one that's been created specially for motion tracking. Now you don't do your tracking in the Composition panel; you need to do it in a Layer panel. Just take the layer that you want to track and double- click it to open up its Layer panel and you see that the tracker controls now become active. You can either track motion or stabilize motion. Let's do a track.
After I click one of these buttons I get a Track Point. The inside of this is the feature region. It defines what actually want to follow up in this image. The outside square is a search region. How far and wide I look to try to find that feature that I am tracking from frame to frame. As you move the cursor over the track point boxes, you will see a few different icons appear. These reflect different ways of moving the Track Point. For example, if I move my cursor in between the boxes you will see a four-way arrow here at the edge.
That means I am going to move the Track Point as a whole. And as I move the track point the center, the feature region is magnified. There we go. If I want to resize a box rather then use I can go ahead and move it to particular corner and you will see the all four corner move symmetrically or move it along an edge and you will see that I moved with box as whole as opposed to corners. I will go ahead and move my feature region inside and then move my search region on the outside.
If you need to further tweak your Track Point, hold down the Command key on Mac or Ctrl key on Windows and drag at individual corner to get it exactly where you want it to be. The size of these boxes is just as important as the position of them. You want to go ahead and make the feature region just big enough to enclose the feature you are tracking, but not too big. You don't want to pick extraneous features like submit from the background. The search region needs to big enough to follow the movement of the particular feature I am tracking from frame to frame, but not so big that it takes up the whole frame. The bigger the search region, the longer your tracking is going to take and the larger the chances going to accidentally pick up a wrong feature somewhere else inside this region.
So I am going to go ahead and bias it in the direction that I know my wildebeest is moving which is from left to right and then make it as big enough to capture that movement from frame to frame. After I decided what feature it is I am going to track, in this case the horns of the wildebeest. Next comes deciding where I am going to attach the new layer that I am going to have follow this tracked layer. That's where this little Plus icon, the attach point comes from. This says this is where the anchor point of my new layer is going to go. In this case I am making above a text bubble to follow this wildebeest. So just for laughs, I am going the attach point down by the wildebeest's mouth. I am tracking his horns, but the new layer is going to be attached down here in relation to the layer that I am tracking.
Now hand in hand with setting up a good Track Point is choosing good Track Options. I will click on this button to open up the dialog and there are two things in particular that I need to focus on. One is the channel what am I going to be tracking and in this case where the wildebeest is considerably darker than the sky behind, I will go ahead and choose a Luminance. I am going to look for this feature based on how bright or how dark it is. However, if I am in a situation where the feature where I am tracking is the same brightness as the background, but a different color then instead I might choose to track RGB or to track Saturation, but again this wildebeest is dark against medium brightness, Luminance is my better pick. The other thing you need up in your Options is what to do from frames to frame.
Now you do want to track Subpixel Positioning. There is no need to track fields in this footage because it's not drastic movement from field to field. But I do need to worry about whether to adapt my feature. If the size or shape of my track feature is changing a lot from frame to frame, I want to turn on Adapt Feature on every frame. If it's not changing a lot from a frame to frame, I will turn it off. Now when After Effects finds the feature in the next frame, it assigns to it a Confidence reading of how closely it matched its previous picks on what the feature is supposed to be. This pop-up allows you to decide what to do if its Confidence becomes too low. In other words that the feature is changed too much.
You can go ahead and continue tracking no matter what. You can stop tracking which gives you the opportunity to set up a new feature region. You can say well, just Extrapolate Motion, keep going in the same direction. Well, the option I use most often is Adapt Feature that basically says if the feature is changing a little bit from frame to frame until it gets say 20% different from where it was originally then instead see how this feature looks on this frame and now make that the reference that your tracking and click OK.
So those are the two major things to setting up a track: your Track Point and you options.