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Image Behind Person Effect?

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Sypherion AsariImage Behind Person Effect?
by on Jan 10, 2014 at 4:51:29 pm

Hi, everyone. I have this clip of a person and a wall. I also have an image I imported in AE and into my scene to have the effect that that image is now on the wall, like a poster! The only problem is that when the person moves, he moves over to the image, and then the image goes over him, clearly ruining the effect that there is a poster on the wall.

I've been looking for a way to somehow maybe isolate the person so that every time he moves, his body overlaps the image so that it looks like he is in front of the image on the wall.

I haven't found a way to do this yet even though I thought this would be a basic technique. Does anyone know if it is possible to do this?


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Chris EvansRe: Image Behind Person Effect?
by on Jan 10, 2014 at 5:11:09 pm

What you are trying to do is called rotoscoping.

My best advice: just google it. (or bing it, I suppose, if you're one of those)

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Matt DavisRe: Image Behind Person Effect?
by on Jan 10, 2014 at 9:46:07 pm
Last Edited By Matt Davis on Jan 10, 2014 at 9:47:21 pm

Yes you need to isloate the person.

The easiest way to do this is on a green/blue screen. Depending on what the wall really looks like, you might be able to do a rough colour key, but it's unlikely that life will be that easy.

So what you have to do is create a mask around the person to insert themn on top of your wall with poster or around the poster to remove it as the person walks over it. In After Effects, as in life, there are many ways to skin a cat. But I'd likely go with isolating your person.

Bascially you'll go through your footage and ensure that for every frame of video that your person is in front of the poster, the mask is covering the person and not covering the poster. It's important to be precise in areas where they cover the poster but not so much in other parts of the scene, if they don't change.

Of course if you isolate your person, you'll lose the wall entirely, so you'll need a way to have your wall, with your inserted poster, in a layer underneath your person. Again, many ways to tackle this. If you have footage of the wall wihtout the person, the easiest is to insert the poster on it and place that underneath the layer with the person in it.

For tips on rotoscoping, there are literally hundreds of tutorials on YouTube.

Best of luck!

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Todd KoprivaRe: Image Behind Person Effect?
by on Jan 11, 2014 at 5:56:29 am

Start here for the basics of compositing with After Effects:

Todd Kopriva, Adobe Systems Incorporated
After Effects quality engineering
After Effects team blog

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Sypherion AsariRe: Image Behind Person Effect?
by on Jan 12, 2014 at 1:34:31 pm

Ok, I'm a bit of a beginner, so I thought there might have been an easier way, but I suppose not. Thank you all for your help!

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