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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 this next set of movies rather than have one layer track a feature of a piece of footage, we are going to have an effect track a feature and an underlying piece of footage. If you have access to the Project Files go to the Comps folder and open up 03-Effect Track*starter. Go ahead and drag the Current Time Indicator through this footage to become familiar with it. It's a helicopter fly by a series of peaks along the top of this mountain. Let's say we want to pretend that some radio signals were emanating from one of these peaks. Well, to do that there is an effect called Radio Waves.
Go ahead and select that and drag it onto your footage. Now, initially it seems like nothing happens, everything went away, but if you RAM Preview, you'll see that Radio Waves emanates a series of concentric circles over your footage. I'll Stop, press End to go to the very end of this footage so I can study what Radio Waves is doing over time. The first section we're going to study is Wave Motion. That determines how the waves propagate out from their central Producer Point.
This is looking a bit light on the number of waves for me, I'd like to have more, so I am going to go ahead and increase their Frequency to get more waves. If it seems to be adjusting too quickly, you can hold down Command on Mac or Ctrl on Windows to adjust by finer increments; maybe I want it somewhere around here say. Another issue is, am I happy with how fast those waves are coming out from the center? If I think they are coming out too fast and therefore going off the edges of the screen too quickly, I can reduce the Expansion so they don't move away quite as quickly.
So I am going to bounce Expansion against the Wave Motion and Frequency of how fast they are being produced, somewhere around there. Another small issue is that these waves are staying on for their entire lifetime as they go outside my Comp panel. Let's say that I want them to fade away, so that after they are produced, we see them just appearing into the ether. Well, to do that I just need to reduce the Lifespan parameter. I take that, pull it down until I have a nice set slowly fading away rings for my center Producer Point.
Now that I have a Wave Motion that I like, let's start playing around with the Stroke or Profile of those waves. Waves dissipate the further they get away from the source. They tend not to stay exactly the same size. So in this case, I am going to reduce the Start Width to a fine line and increase the End Width to a point where they get thick the further they get away. And I have other options in here as well, such as Opacity, Color, and even the Profile or Shape. For example, a Sine Wave creates a more rounded sort of wave; a Triangle has a harder peak in the middle, but we'll stick with Square for now to make sure these are nice and visible.
In addition to producing waves from a Producer Point, a really cool feature of Radio Waves is that it knows where the Producer Point moves over time. So put your Current Time Indicator back at the start of the Comp, go into your Effects Control panel, look for that Producer Point, and Enable the Animation Stopwatch for that parameter. Go a few frames later in time, I am around 2 seconds myself, and drag that Producer Point somewhere else in the Comp. And now you will see you are dragging the creation of those waves to this new point.
If you're having trouble seeing that Producer Point, go ahead and use the Crosshair parameter here to relocate it, or just go ahead and scrub its values. Go a little bit later in your Composition and place another keyframe, such as say maybe around here. Now when you RAM Preview, you will see that each new wave expands out from where it was created, but since the Producer Point is animating, each new wave is being created from a different point in space. That's what creates these really cool overlapping patterns.
Well, we are going to take advantage of this by attaching that Producer Point to one of those mountain peaks by using the Motion Tracker, and that's what we'll do in the next movie.
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