Join Mark Christiansen for an in-depth discussion in this video Effectively track motion, part of After Effects Compositing 06: Tracking and Stabilization.
- I don't know this for sure, but I think a lot of people give up on motion tracking in After Effects after the very first attempt because it's awkward. So in this lesson, I'm going to give you the cleanest approach to tracking this screen, so that it matches the motion of this phone. Now the first step is just to analyze what type of track we need here. I'll open up the background scene, which is what I'm tracking. And I can right click, and say Track Motion.
That brings up the Tracker Panel, right here. There are several different options, some of which are the automated Track Camera and Warp Stabilizer, but then Track Motion and Stabilize Motion actually use this Point Tracker, and that's the one we just set by default. Additionally, we can choose a track type. Now you could assume in this case, that we need, for example, a Parallel or Perspective Corner pin to get the four corners of the screen.
That's really overkill, and a bad idea. In fact I don't really like the corner pin tool. I would suggest that since there's effectively no rotation happening here, all we need is a point track. So, now that I have my track point, I can just press the forward, since I'm at the beginning, play button. I can track forward or backward throughout all the frames or frame by frame. I'll just press Analyze Forward. And you can see it's having some trouble.
The one thing you always need to do with the Motion Tracker is set the first point. Now it doesn't have to be at Frame 1. We could go out here in the middle, but I'm looking for a point or a corner, and there's several things here that would do. I'm going to align them with my cross-hair, and I kind of like just this corner where the lighter colored screen meets the darker colored phone. Now sometimes on a shoot, you see people put green tape, etc. on screens.
This should show you how you really don't actually usually need that. Watch how successfully this tracks, as soon as I set it. You can see as we zoom in, that it's tracking at the sub pixel level, so you can see the pixels, and you can see those track points are falling in between them. That was only part of the track of course. So I can also track backwards, since I started in the middle. And now, I have all of the motion.
Fantastic. So now what? Well now I apply it to the target. Now, in this case by default, it has chosen the top layer, and that's really the only choice. But I'm going to give it another choice, by adding a New Null Object, and I'm going to call this Screen Track. I'll choose it under Edit Target. Say OK, and Apply.
I always get asked X and Y, and I will say Yes. And now I'll just go back to the beginning, if I unhide my controls, I can see that I now have a null that follows the motion of the screen so all I have to do, is pair the screen layer to that null layer. So I'll reveal the Parenting Controls. I can select them here under Columns, or I can use Shift F4 to toggle them on and off. And I'll just parent Foreground Screen to Screen Track using the pick whip, and now it follows the motion of the track.
Now notice that I didn't position the screen quite correctly. This is where setting a null is a huge help. If, for example, I were to move the null to fix the position of the screen, what I've just done is messed up my track. And that's why I didn't apply it directly to the screen layer, because I don't want to move around layers that I've already tracked. So instead, I'm actually going to lock the null layer, and I'm free to move around the screen layer instead.
This is the main reason that I set that null. That looks pretty good. I'll just double check. A little more nudging... And there we have it. So, if this lesson offered no earth-shaking new knowledge to you, congratulations, you are already using the most straightforward methodology to track your shots.
One final note, you may have noticed that this is a 3D layer, but it's a 2D track, so I only use 3D in this case just to rotate the screen around to match the orientation of the phone. So now, let's move on to some trickier situations.
Here, Mark Christiansen shows how to use the five different After Effects trackers, customizing them to work best in the situations that motion graphics artists encounter most often. He covers the fundamentals, as well as opportunities to think outside the box, especially when an automated approach won't work.
- Why point track?
- Recognizing trackable points
- Offsetting a tracker
- Applying the track to a matte
- Using nulls and third-party scripts to create track mattes
- Tracking and stabilizing objects and planes
- Automated tracking
- Applying 3D tracks