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Tracking an image to a piece of paper

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Rob JenningsTracking an image to a piece of paper
by on Nov 20, 2011 at 2:17:56 am

Hey guys,

I'm sure this is going to sound very straight forward, but I'm totally lost and could use some advice.

I'm working on a project that involves tracking a video to a piece of paper. We have an OTS shot of a girl holding the paper, and the video goes from a still image printed on the paper to a moving video. Our paper does have several tracking dots on it.

I'm having trouble using the dots to track the movement of the paper and applying it to the video to get a realistic move through 3d space. It wouldn't be such a problem if it only moved through 2d space, but it rotates slightly between frames, thus exaggerating the problem.

If anyone could spare a few minutes to give some advice for approaching the problem I would GREATLY appreciate it.

Thanks in advance.


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Jamie FranklinRe: Tracking an image to a piece of paper
by on Nov 21, 2011 at 9:31:47 am

Did you track position and rotation? Sorry to ask but I've forgotten sometimes to click rotation on a track.


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Walter SoykaRe: Tracking an image to a piece of paper
by on Nov 21, 2011 at 2:58:05 pm

You may be better off using a planar tracker like Mocha, rather than AE's built-in point tracker.

Mocha is designed specifically to work with 2D planes, like a sheet of paper. Mocha-AE is included with After Effects, starting with CS4.

If the paper bends in the shot, you may have to try to match the distortion by hand.

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog - What I'm thinking when my workstation's thinking
Creative Cow Forum Host: Live & Stage Events


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Rob JenningsRe: Tracking an image to a piece of paper
by on Nov 21, 2011 at 4:42:58 pm

Thanks for your input, guys. I did find some articles on Mocha, and tried it out. (I haven't used After Effects since CS3, so I didn't even know about Mocha). However, because we prepared the shot to be processed with After Effects' point tracking system by placing dots on the paper, and did not provide distinct definition on the corners of the paper, Mocha had trouble tracking the points. (The paper is on top of a white folder, so the indistinct white-on-white is virtually impossible for a computer to track. Thus, I tried doing it by hand, either using the autokey function or by adding keyframes on each frame of footage, and adjusting the plane by hand. So I do spend about an hour doing this, then go to play it back, only to find the keyframes no longer represented what I set up at all! I found that every time I adjusted a point, that adjustment would affect every frame before it.


What kind keyframing is this?? Is there something I'm missing? Is there a way to manually set the surface of the plane on each frame in Mocha?


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Walter SoykaRe: Tracking an image to a piece of paper
by on Nov 21, 2011 at 5:13:33 pm

I'd recommend asking your Mocha questions in the Adobe After Effects forum [link] -- there are a couple Mocha heavy hitters who may be able to help better.

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog - What I'm thinking when my workstation's thinking
Creative Cow Forum Host: Live & Stage Events


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