Point tracking

- The simplest way to get one layer to follow along with an element in a shot, is to use point tracking. We need to identify a unique area to track that stays in the frame for the duration of the shot. Let's have a look. Here in this composition our background plate has plenty of tracking markers and it was obviously intended to insert different elements into the shot. And here I've incorporated some curtains with the logos in the background. And I was able to do this using point tracking. So, let's start with this blank start composition.

And you'll see that as we scrub through what we want to look for is those tracking marks. Anything that has high contrast, a unique shape, something that definitely stays in the frame during the entire duration of the shot. So these guys down here probably won't qualify as they start to exit frame. But because we're inserting these curtains, let's go ahead and track these guys over here. So, they're bright, they're contrasty and with layer one selected, let's go ahead and right click and say track motion.

Now, in the middle here, of our layer window, we have a track point. Let's go ahead and zoom in and you'll see that the track point has two squares and a cross hair in the middle. Let's work our way from the outside in. This outside square is the search region and as after effects goes from frame to frame it's going to look for this area and search for specific feature inside here. And that feature is defined by this smaller square here. So, let's go ahead and move this entire track point over. I'm going to click in the middle here, of this small square.

And you'll see that we get this magnifying glass to help us easily identify our feature area. And so as I hover over, let's go ahead and move and select this guy here. What we want to do is make sure and resize these feature areas to focus in on just that marker. And we'll readjust our search region to accommodate from frame to frame. Now as we scrub through you'll see that there's not much movement from frame to frame so our search region doesn't need to be so large. If it was a drastic movement then we would probably need to increase the size of our search region.

So somewhere in here's probably good. And we're probably only going to need about five seconds of this. Let's go ahead and make that happen. We'll right click on our work area and say trim comp to work area. And now lets go back to the very first frame and over here in our tracker panel you'll see that we have track type transform. And we have position selected. We also have the ability to track rotation and scale, but for this example let's just go ahead and leave that for position. And we want to analyze forward. So, starting at the first frame we'll hit analyze and after effects is going to do its thing.

And at the very end here you see that we have track key frames. And what we want to do now is attach those key frames to something. Let's go ahead and in our assets folder, let's select null one. And we'll bring this on top and back in our tracker panel let's go ahead and say motion source. Let's re-select our warehouse rally plate and down here under edit target let's make sure that we're going to apply this motion to layer one. So we'll confirm that and we'll say apply. After effects wants to ask us, do we want to use both X and Y positions? Yes we do.

So now you see that null one just jump into place and as we preview this, you'll see that the null is tracking it's position along with that tracking marker. So that's great. All we need to do now is insert our curtain. So let's go ahead and bring our logos composition in here. That's entirely too large, wouldn't you say? We'll size this down a little bit and as we zoom out, you'll see as we scrub through we need to attach that layer to null one. If you don't already have it enabled, go ahead and reveal the parent column by right clicking on an existing column and you'll say columns and enable parent.

So now this way what we can do is select layer one and tell it's parent to follow along layer two. And now that we've done that you'll see that the layer itself is tracking along with the scene. So this is just position information that we're tracking. We can also track rotation and scale. Let's go ahead and move over to our paper airplane example. And you'll see that this paper airplane has a camera move behind it, so it's scaling. This paper airplane is also rotating and moving in position. So, let's go ahead and track this.

So, we'll select layer one and say track motion. And in here we're going to select position, rotation and scale. And instead of one track point, we now have two. So, let's go ahead and re-position track point one to this corner point right there and we'll do the same thing for track point two. Now as we scrub through, you'll see that there's a lot more movement, more drastic movement, and so we're going to want to increase our search area considerably. In our feature region, let's go ahead and leave that somewhere in there. Do the same thing for track point two.

Now, when we analyze forward, paper airplane will grab all that information and apply it to something else. So, let's go ahead and stop right there. And let's do the same thing that we did previously. We'll take a null and we'll make sure that we select layer one. We'll go back to our motion source and say hey reference that tracker. And we'll edit the target, just confirm that it's null one. Yes. And then we'll apply. Yes again. And you'll see now that if we put null one on top we have a null object following along with that paper airplane.

Alright. Cool. Let's go ahead and add something to attach to this paper airplane. And I've got some 3-D missiles here that I thought might be neat to attach to a paper airplane. So, let's go ahead and add this missile composition to our paper airplane comp. And we'll add it right on top, for right now. And all we need to do is just reposition this so it's kind of centered. And then we'll take layer two and parent it to that null one. And now we're getting some missiles that are attached to that paper airplane. And to really sell this effect, let's go ahead and duplicate layer three, which is our background layer.

And we'll put it on top of the missiles and this time we'll just search for the extract effect, put that on top, and here in the luminance, these black point values right here, we're going to nudge this over and as we slowly nudge them over we're actually keying out just the paper airplane and creating transparency. So, we're putting that on top of the missiles which is on top of the background. And just like that we have a heavily armed paper airplane. You don't want to mess with that guy. So there you have it, with point tracking you can extract position, scale and rotation information from some portion of the footage and incorporate other elements into your composition.