Join Richard Harrington for an in-depth discussion in this video Tracking an object with the 3D camera tracker, part of After Effects Guru: Tracking and Stabilizing Footage.
Normally the 3D camera tracker is used to track a camera. However, I sometimes find if the camera locked off, and there's movement within the scene, you can cheat and use it as an object tracker. Let me show you how. Let's take this shot of traffic and put it into a new composition. I'd like to obscure one of the license plates here. So using the track camera command, it's going to analyze. It's now solving, and what I'm going to do is select the license plate. So, I can do this pretty easily with some shift clicks and I've got the license plate relatively selected accurately.
Holding down the option or alt key, I'll scale that target a bit smaller and with a right click, create a new solid and a camera. Now that I've got the solid, I'll just use that as an adjustment layer. So it's very easy to adjust the height and the width and with the anchor point, I could nudge that into place so it covers up the license plate. Let's go to the rounded rectangle tool and double click and it even takes on a license plate type shape.
I'll feather those edges just slightly, so they blend a bit and then remember, any layer can become an adjustment layer by simply clicking the Adjustment Layer switch. Now, I could toss a blur effect on there and by blurring that out with the repeated edge pixel, you'll notice that even though the camera didn't move, I was able to cheat and use that as an effect to obscure the license plate. Now, you could, of course, with the same shot selected, tackle another car.
So, with the 3D camera tracker active, I could attempt to find this license plate. Remember, dragging to different points may show you more or less. There's a lot of points there right now, there we go, make that a little larger and do the same thing all over again. Create a solid. Scale that, as needed Adjust the anchor point to position it. Toss on the rounded rectangle, make it an adjustment layer and apply the blur. Now, what you're going to notice is that because these two cars are moving at different rates, it's not going to be perfect.
Right now, everything's more or less fine, other than we're blurring out part of this vehicle here. So, what I want to do is make a slight change. Right about here, is when the car behind actually moves. So, p for position, I'll just add a key frame,. And nudge that just a little bit and then it's pretty easy to mask that mask. So if I select the mask, I can take the pen tool and click to outline the shape of the car.
We'll tell that mask to subtract. So, now it removes from the other mask, leaving the car behind and it's pretty easy to just keyframe that. So as the front car moves off, command T for free transform and just sort of pull it along with the vehicle. Making sure, of course, that you get it all the way off the screen, before the truck comes into play.
Now this is not perfect, but from a very quick down and dirty, I've got two tracking points here, I've managed to obscure the license plates and as this car pulls off, it reveals this other mask down behind. You can continue to refine the feather here on this mask, and make other slight adjustments; but as a quick solution for obscuring things like license plates, or name badges, or logos, this often works. This is not the official way to use the 3D camera tracker.
In this case, I'm using it as an object tracker. But, my feeling is, is if it works, why not give it a shot? In this case, it saved a lot of time, and it gave me results that were good enough. Particularly, if I was on a tight deadline for something like a broadcast news piece. So feel free to explore with the 3D camera tracker, and you might find some unexpected uses that takes it that much further.
- Analyzing footage
- Using the 3D camera tracker to stabilize footage
- Choosing and moving a target
- Adding 3D text to a scene
- Tracking an object
- Applying the Warp Stabilizer VFX
- Choosing a stabilization method
- Reducing rolling shutter distortion
- Matching movement