Hello and welcome back to KnowledgeCity's After Effects, intermediate course. I'm your instructor, Tim Jones. In the last lesson, we talked about call-outs and created one for slide six. Going back to the completed video, you'll see that when this call-out appears, it points to the very edge of the astronaut's shoulder. Then follows him as he walks up the incline. So how did I achieve that effect? Well, if you I've been paying attention to the call-out text, you probably already have the answer. I used motion tracking! In this lesson, we're going to review how to use the point tracker in After Effects. Point tracking is a commonly used motion graphics technique. It can be used to attach objects to your scene, such as this call-out example. Or replace graphics, such as replacing images on say, a cell phone in someone's hand. Here's how to use the point tracker. In my slide six comp, I'll double-click into the media 1 comp and we'll see the astronaut stock footage. so we know there are some effects being applied to the footage in the slide six comp. In general, point tracking works like this. You pick one or more points on a video, go frame by frame through that video to assign the point of each frame, and then apply that motion to a null object. Then you can use that null object as a parent to one or more layers. In this example, we're going to do single point tracking. In other words, I want to know where one point is in each frame of this video. For this video, I'll choose the very edge of the shoulder pad of the astronaut. First, I'll create a null object. I'll go to the top menu, select layer, new, null object. Next, in the top menu, I'll click animation, track motion to open up my point tracker. And track 0.1 will appear in the center of the composition window. Let's zoom in and you'll see that the point tracker actually has three objects. The center or point, and two bounding boxes. The X at the center is the attach point and is the actual point being tracked. The small box is called the feature region, which defines the object. And the larger box is called the search region, which helps After Effects put that object within context of the video. Hover over the point tracker until the four-way arrow icon appears, then drag everything to the object you want to track. I'll choose the very point of this shoulder pad. In your tracker pallet, make sure that track type is set to transform and then only position is checked. Also make sure your target is set to null object you created. Now you can tell AE to analyze the footage. You can use the play controls to analyze forward or backwards from your current time indicator. Or you can analyze one frame at a time, forward or backwards. You can always go back and fine tune the point tracker later. So I'll just hit play and let AE do its work. When that's done, I'll check that the target is set to my null object, and then click apply. Now if I open up the transform properties of the null object, I can see a key frame for position on each frame. And if I scrub the timeline, I can see the red box here follows the astronaut as he walks up the incline. Next, I'll drop the 03 call-out comp on top of my video and move it so that the pointer is directly over my tracking point. Finally, I'll grab the pick wick in layer two, drag it to the null object in layer one to set it as my parent layer. Now if I scrub the timeline, you'll see the call-out seems to emerge from the tip of the astronaut's shoulder and follow him throughout the shot. Let's go back to slide six and scrub the timeline to see how that looks. And I see two problems right away. First, the call-out is appearing too early. And second, its lost its color. Let's take those one at a time. First, I don't want the call-out to appear before we cut in tighter here. So I'll position my current time indicator, just where that cut occurs, then double-click into the media 1 comp. Now I'll slide the call-out comp to start here. Let's go back to the slide six comp to see how that looks. Okay, I'm happy with that. Now let's fix the color issue. I'll twirl open the media 1 layer and see that there are effects being applied. Now what we really want is for these effects to be applied to the video layer, but not the call-out. So I'll select the effects and click Ctrl + C on my keyboard to copy them. Next, I'll double click into the media 1 comp. Select the video layer at the bottom and click Ctrl + V on my keyboard to paste those effects. And voila! This is how I want my scene to look. Now going back to scene six comp, I'll turn those effects off for media 1 and we're back in business. And that brings us to the end of our lesson on motion tracking, thanks for watching.
