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Static Shot, remove part of the background
Hello people at creative cow
I’m trying to figure out a more elegant way to remove a painting on the background of a static shot, where the acting person in the foreground is covering part of the painting from time to time.
What I learned in this forum is to build an alpha channel through superimposing a still frame of the (person-less) room with the shot (blend mode: difference, then apply threshhold) and using this luminance-only result as the source for an image mask on the actual shot (source: luminance). By this ‘difference matte’ the moving person is keyed an I could replace the complete background with a painting-less version.
But I think there has to be a way, where there’s not the full video being harshly processed, but only the part where the picture is, right? Does anybody have another solution because my brain hurts right now..
Thanks!
Chris -
5 Replies
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What you’re doing is what I’d think of as the “quick and dirty” way of getting the job done. Another approach would be just replacing the painting and animating a mask around the actor as needed. If you’re determined to do it within FCPX then you could do it all by hand with a shape mask and keyframes or CoreMelt have their SliceX plugin that can help automate the process.
Going beyond FCPX that are a lot of tools specifically designed to get the job done that would make life easier… Mocha, either full version or the lite version that’s in After Effects can help automate the tracking and masking. AE also has the RotoPaint tool that should make the job relatively painless.
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Jeff Kirkland | Video Producer & Cinematographer
Hobart, Tasmania | Twitter: @jeffkirkland -
Thanks, Jeff,
I thought of masking the head of the person as well (I have motion, so it should be possible), but how do I achieve the head not being cut out and the background coming through, but the head staying in front of the ‘wall-fill-in’? (I think this is a common keying-mind twist..). So if I get this point clear, I can probably use a difference matte for the region of the painting only, which would provide an accurate key without animating a shaped mask or processing the whole video with the matte.
So how do I configure a mask for staying on top, rather than becoming transparent and letting the background pass through?
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Yeah of course inverting the key and putting it on top of everything..
Sorry.. -
Guys, FCPX now has content-aware fill; this can “auto-rotoscope” out a lot of things. You might try it out on this.
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Hi,
I was wondering if you had a good solution to your problem. I’m looking for the same kind of operation: remove a background. I did the difference as a mask technique but it really looks ugly since a part of the image still appears in the difference object (I don’t know if it’s clear). Pixel films is having a plugin that removes the moving object in front of the background, not the opposite. Isn’t there a better technique today?
Thanks if you can help.
Best
Samuel
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