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Layers question

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Roy GuinnLayers question
by on Mar 7, 2011 at 4:58:23 pm

Sorry for the noob question, I just started learning AE. I have several animated clips that I am trying to composite. A base layer, and several foreground characters filmed against a green screen. The base layer was filmed with a short camera pan at the begining. My problem is that when I lay the foreground characters in they are linked to the base layer and pan with it. I want the foreground to remain stationary, while the base layer pans over them. Thanks for any help.

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Subhash NaveenRe: Layers question
by on Mar 7, 2011 at 6:04:32 pm

Hi Roy

Was the camera pan done using After Effects Camera or the footage was shot with the pan? Ideally as they are separate layers, the foreground elements should not be moving with the pan on the back ground layer. can you please post a quick small render?

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Michael SzalapskiRe: Layers question
by on Mar 7, 2011 at 10:56:03 pm

Are you saying that in your background footage the camera was moving when it was filmed and you want your greenscreened elements to match the movement of the background so that it appears they're actually attached to the ground? (What I think you meant) Or are you saying that your foreground characters are linked/parented to your background layer? (which is what you actually said)

- The Great Szalam
(The 'Great' stands for 'Not So Great, in fact, Extremely Humble')

No trees were harmed in the creation of this message, but several thousand electrons were mildly inconvenienced.

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Roy GuinnRe: Layers question
by on Mar 7, 2011 at 11:12:24 pm

LOL I think I followed all that. I posted a short clip but it hasn't cleared the gate keepers yet. The base layer, which is the background, has a short pan at the begining that was part of the shot footage. It was then droped into AE with nothing else done to it. The forground characters, meant to be a crowd at the bottom edge of the screen, were filmed against a green screen and layed over the background. I checked that the two layers are not linked in AE, however the animation responds as if they are. The crowd should be slightly off camera at the begining and come into view as the background pans toward them, so that they look like they are in the environment. What is happening is the crowd is panning with the camera. Very confusing since the pan itself is part of the shot, and not an effect in AE, and the crowd is a different layer alltogether.

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Joey ForemanRe: Layers question
by on Mar 8, 2011 at 1:03:23 am

That's just because they are stuck at the side of the comp where you positioned them. They were shot against the greenscreen with a static camera, so of course they're not going to move out of the frame. You positioned them in your comp, presumably on one side. The camera is moving in the layer below, so that creates the illusion that they are moving with the camera. But they're still on the same side of the comp.

AE has no way of knowing how the camera moved in your background footage.
You have to tell it how, and the way you do that is with Motion Tracking. The motion tracker built into AE works for some types of shots, but for much better results you'll need to learn how to use Mocha, which has shipped with AE as a separate application since CS4.

Since you want your keyed characters to come into frame from offscreen, your shot presents an additional challenge - offset tracking.

Here's a bunch of tutorials to get you up to speed.

Now, if you don't care much about how realistically they enter the frame, you could just manually keyframe the position of the keyed layer to move into frame, and try to match the speed of the camera. You might get lucky and get a believable result. If not, time to dig into Mocha and enjoy the magic.

Joey Foreman
Editor/Compositor/VFX Artist

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Roy GuinnRe: Layers question
by on Mar 8, 2011 at 2:44:59 am

Well, like I said from the get go, I'm a bit out of my element in AE, just jumped into it and I feel like a fish out of water. But thanks for all the feedback, and the direction to the tutorials.

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Dave LaRondeRe: Layers question
by on Mar 8, 2011 at 3:34:56 pm

[Roy Guinn] "I'm a bit out of my element in AE, just jumped into it and I feel like a fish out of water."

That's an entirely understandable feeling; there's a LOT to learn in AE.
But there are ways to learn the basics, upon which all AE knowledge is built. Such at this:

And for the cost of a new video game, you can get something much better:

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA

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