Point tracking

- [Instructor] Motion tracking is an important part of Visual Effects Compositing. Motion tracking allows you to detect the motion within one piece of footage and apply that motion to different pieces of footage so it looks like everything was shot with the same camera. For example, with this project, if you play it back, you'll see the background moves. The camera that shot that tilts and pans towards the end. The camera that shot the cat, again, screen screen is static. So it might be nice to detect the motion within the background and apply it to the cat. There are two ways to approach motion tracking and silhouette. One is to use a tracker node that's included in the transform category. The other is use the same tracker function that's built into some nodes, such as the Roto node. Let's start with the tracker node itself. I'll drag it into the scene because we want to detect the motion within the background footage, I'll branch off the bird footage connected to the tracker. Once you do that, you'll see there's a tracker tab right beside the timeline. The tracker node actually provides three different trackers. There's a point tracker, planar tracker, and mocha tracker. We'll start with the point tracker. The point tracker is a transform tracker, which means it detects motion in the X and Y direction. In other words, the left right, up down direction. And that's fine for this footage. In contrast to other trackers, it doesn't provide a tracking point to start with. You have to create the first one. There's a create button for that right here. I'll click that. I get a tracking point in the center. I'll zoom in so you can see it. The tracking point has a center crosshair, you can click drag. There's an inner box, which is the pattern region. And this establishes the pattern that's tracked over time. It also has a dotted outer box, which is the search region. And this is where the tracker goes if it loses track of the pattern. So let's find a high contrast detail to track. You also want a pattern that's not occluded and doesn't leave the frame. Top of this spire will work quite well. I'll place this at a corner. You can click drag the edges or corners of the boxes to change your size. The larger pattern will lead to more accurate tracking, but will take a little bit longer. Now, if you wanted to track rotational or scale changes, you'd need to add a least one more tracking point. You'd have to use a create button. We only need to track left right, up down motion. So we don't need a second tracking point right now. We'll talk about tracking rotation scale later on, but for now we're good. Before I track though, I do want to mention one very nice feature. And that's the preprocessing section. This allows you to adjust the footage just for the tracker and it's non-permanent. For example, I can turn on the preview and then adjust the contrast slider to give it more contrast. And greater contrast will be easier for the tracker. I'll turn off the preview for now. We're now ready to track. I'm on the first frame so I'll use the track forward button. It tracks quickly. When it's finished, you'll see green key frame tick marks on the timeline. You'll also see a green motion path. This represents the movements of that pattern over time. Now, the pattern is a bit bumpy and lumpy to start with, and things like video noise, film grain, motion blur, and even the soft foreground snow can interfere with the tracking. So it's not quite as smooth as we may like it. Luckily, there is a smooth button to simplify the curve. It's down here. If I click that, I get a slider. If I raise the slider, the motion path is simplified and becomes smoother. I don't want to go too far, so maybe about a third of the way up. Now, this is a permanent change. If you were to save out the project, that motion path would be permanently smooth. If you haven't saved out yet, you can simply undo, Control or Command + Z. And of course, if you wanted to, you could retrack to get fresh key frames. This is good for now. Let's play it back and see how it looks. If you watch the crosshair in the pattern box, that follows quite nicely. So now we have good tracking data and we can think about how to apply it to a different piece of footage. And that'll be the next step.