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Explore how to use the motion tracker and stabilizer built into After Effects and shows how to handle a variety of shots. Author Chris Meyer leads a quick tour of the third-party software mocha and demonstrates the workflow for The Foundry's KEYLIGHT, both bundled with After Effects. The course also covers tracking a greenscreen shot with a handheld camera and replacing its background.
The After Effects Apprentice videos on lynda.com were created by Trish and Chris Meyer and are designed to be used on their own and as a companion to their book After Effects Apprentice. We are honored to host these tutorials in the lynda.com Online Training Library®.
In the previous movie, we tracked our original 2D footage and used this data to create a 3D camera and a Null placed on the plane where we want to place our brand-new object or layer in After Effects. In this case, we want to place this poster. I'm going to enable the poster's 3D layer switch because I wanted to be in 3D space so it reacts to the 3D camera. I need to reveal the Parenting column to attach this poster to our Track Null that we created.
You can right-click on any of these column headers and choose Parenting, or you can use the shortcut key of holding Shift and pressing F4 and then you'll get your Parent column. With my poster still selected, I'm going to click on its parent pop up. And in doing so, you'll see some text appear in your timeline that is new to After Effects CS6. It's a little helper that tells you, you can hold the Shift to move a layer to the location of its parent. In other words, it would zero out any position offset from the parent which is a very handy thing for 3D Tracking, and this is a new feature they added in CS6 to go along with 3D Camera Tracker.
Or another option, which is hold Option on Mac, Alt on Windows, which will keep any animation movements, etcetera that the child has, but offset them to the position of the new parent. In this case, we want to do Shift parenting. So I'm going to hold down the Shift key and select Track Null 1. By doing so you'll see the poster has now jumped to the location of our Track Null that we had in this composition. And I'm going to actually drag my Poster layer to be underneath the Null layer so that they're visually grouped together in the Timeline Panel.
Now one idiosyncrasy of the 3D Camera Tracker is that it does not really know where the ground plane is, so things can be oriented a bit oddly when you first create Track Nulls. I'm going to divide up my work here to make the Track Null have the correct position and orientation to match the side of this building, but then I'll work with the Poster layer to rescale it into any other specific modifications to that layer to make it match to the size of the building. By playing around with the orientation of the Track Null, R is the shortcut to reveal these parameters.
I have it all set up in case I want to parent another layer to it later. I have found that almost all the time, when you have a Track Null, the first thing you need to do is zero out the Z orientation. That's the obvious rotational offset that this poster has in relation to that building. I'll press zero and it's already massively better. I'll then select my Poster, press S to reveal Scale, and scale it up to be the size I wanted to be in relation to the side of this building. Now again, you're not necessarily in trouble by scaling a 3D layer over 100%.
The big question is, is it still the same size or smaller than it was as the 2D layer? And if you remember that poster originally was quite huge in this composition, so I'm still good here. Okay, let's look at it through this scene. It actually holds up pretty darn well. I'm seeing a couple of small things here though. One, the poster is a bit high in the frame. So in this case I can move either the Null or my Poster. Since I might want to apply different posters to the side of this building later, I'm going to go ahead and move the Track Null.
So I'm going to select it and carefully move its Axis arrows. I'm in Local Axis Mode so these axes are based on the position of that Null object. By doing so, I can be very careful and constrain my movements to say just the Y-axis or just the X-axis relative to my placement on the side of this building. The other thing I'm noticing is the poster is tilted a little bit in the Y dimension. You notice that this corner of the poster is closer to the window than this corner of the poster is to the far window, and the same down here.
So I'm going to hold Command on Mac or Ctrl on Windows and very carefully scrub the Y orientation of this poster in small increments, just to make it lay better against the building. It's going to be hard to get this absolutely perfect. For example, your underlying scene may have lens distortion in it which will throw it off. And indeed, a good prep step is to remove any lens distortion in your footage ahead of time and After Effects has an Optics Compensation effect to help do that for you. But for the sake of this tutorial I think I'm already pretty darn close.
I'm going to press zero on the numeric keypad, cue up a quick RAM Preview, and I'm reasonably happy with the tracking of the shot. I think I might make the poster a little bit smaller so that it doesn't overlap the edge quite as noticeably early in this shot. So I'll scrub it down a little bit. Again, you can hold Command or Ctrl and scrub by smaller increments. Preview again.
Not a bad track. You can spend a lot of time getting that extra one-tenth of 1%, but for the sake of this tutorial we're pretty close. Finally, I like to take steps to better blend or better composite my new layers onto the original footage. One of my favorite tools for this is Blending Modes. Now here is something to keep in mind in After Effects CS6. You now have a choice of different Rendering engines; the Classic 3D Renderer formerly known as the Advanced 3D Renderer or the Ray-traced 3D Renderer introduced in After Effects CS6.
The problem with using the Ray-traced 3D Renderer is that you lose a lot of compositing functions in After Effects. I'm going to select it, click OK, and I get a Warning dialog that the following features are not rendered by the Ray-traced 3D Renderer, including Blending Modes which are one of my favorites. Track Mattes were also used full if you're trying to use this object to maybe crop off something else you're putting in that building. So I'm going to go back and convert this back to the Classic 3D Renderer so I can go ahead and use Blending Modes.
I'll press F4 to bring up the Blending Modes column. You can also click on the switch at the bottom of the Timeline Panel. And I like modes such as Overlay, Soft Light, Hard Light as a starting point to see how it blends that building. That's a little too colorized. Meanwhile, Hard Light doesn't quite give me what I want, although I can see the windows through the poster, which is a nice effect. These posters tend to have lots of perforations in them so that people inside the offices can look out and so the wind doesn't catch them and blow them off the building like a sail. Let's try Soft Light.
That's getting closer to the type of composite of a perforated piece of cloth against that building. It's lacking a bit of density or opacity though, so I'm going to go ahead and duplicate that layer, bring up T for Opacity for my copy on top, and either keep both layers in Soft Light Mode or maybe go ahead and put one in Normal Mode and back off its Opacity to get a blend that I want. I think somewhere around there that's giving me the sort of composite that I like. I'll go ahead and cue up another RAM preview here.
Not a bad composite. I'm pretty happy with that. There is a little bit of sliding of the poster relative to the building. I could slightly animate the offset of that poster to keep it where I want it to be. I could also further fiddle with the positioning of the Null. If I'm having too much trouble with the position of this poster sliding relative to the building, I might just have a bad Track Points. I should go back, delete the camera, delete the Track Null, and start over with the different set of Track Points to see if I can get a better track. But this gives you an idea of the procedure of using the 3D Camera Tracker to put a poster on the side of the building.
Okay, that was actually a lot of fun. Let's go further and in the next movie apply some text to the scene as well.
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