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Using DIFFERENCE compositing mode to isolate differences & "clone" people

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Red-Rob Rothkopf
Using DIFFERENCE compositing mode to isolate differences & "clone" people
on Jan 11, 2018 at 7:59:58 am

Hi! I'm looking for guidance on the best way to achieve this effect, either using native VEGAS tools or a plug-in (like BCC "Compositing" mode, or something else??)

DESIRED EFFECT: Be able to film a subject multiple times in a room, and have all of them appear in the image with proper color and levels.

ASSUMPTIONS: I have three clips, all shot with a locked-down camera, wide shot of room . (CLIP A) the wide shot with no subject in the room (CLIP B) only subject 1 walking around the room (CLIP C) only subject 2 (or same subject) walking around the room.

TECHNIQUE THOUGHTS:
  • NOT a split screen

  • NOT masking parts of the image

  • I'm imaging using compositing modes, Vegas should be able to identify all pixels in CLIP B not in CLIP A (essentially masking out Subject 1, and do the same thing to CLIP C (masking only Subject 2), then I could composite both of those results on top of the clean room matte.


  • I've tried playing with modes but honestly just can't figure it out.

    Anyone know an easy and intuitive way to do this?


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    Marco Baer
    Re: Using DIFFERENCE compositing mode to isolate differences & "clone" people
    on Jan 11, 2018 at 9:15:08 am

    Imho, there is no easy way in Vegas Pro. In theory you could use difference masking to create a black & white mask and use this mask again with another FX and compositing modes to get close to the desired result. But actually the slightest shadow (and even noise) would make this a hard job.


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    Red-Rob Rothkopf
    Re: Using DIFFERENCE compositing mode to isolate differences & "clone" people
    on Jan 11, 2018 at 9:38:31 am

    It sounds like you're on the right path... but like you said, converting it to a B&W mask would potentially cause shadow problems.

    Could you detail out a bit more what your plan looks like (layer-order, compositing modes) to make your idea work?

    Are there 3rd party tools that could help accomplish this?


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    Marco Baer
    Re: Using DIFFERENCE compositing mode to isolate differences & "clone" people
    on Jan 11, 2018 at 10:25:28 am

    It's a long time ago I tried to do this in Vegas Pro and I gave up because it was so hard to get a clean mask. I don't remember the exact steps to take. Besides shadows and noise, also if forground object and background are close in color and/or luma it would very hinder this process.

    I think you would start with two layers of same shot and apply a difference mask to the top layer. Then you'd start color/luma correcting a parent layer above the two others and hopefully resulting in a clean pure black&white mask. But this is where it most often fails. If it worked you could nest this composition to a new Vegas instance and use that mask project as base for a multiply mask compositing mode combined with the mask fx and fine tune a bit via the mask fx adjustments.
    If you try using the difference mask compositing you could probably guess if this could work or not.

    I thought the Echo FX of HitFilm Ignite would do almost same, but it is different. So without chroma keying I don't know how this would properly work. All these clone fx plug-ins available work the other way round.


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    Red-Rob Rothkopf
    CloneFX plug-ins work the opposite way
    on Jan 11, 2018 at 6:34:02 pm

    I haven't worked with "CloneFX plug-ins". Do they rely on chromakeying, and then essentially duplicate whatever's remaining with various transforms applied?


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    Mike Kujbida
    Re: Using DIFFERENCE compositing mode to isolate differences & "clone" people
    on Jan 11, 2018 at 1:36:48 pm

    See if this very old tutorial is of any help.

    http://matthew.chaboud.com/vegas5/twocats/


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    Red-Rob Rothkopf
    old tutorial for masking and duplicating composites
    on Jan 11, 2018 at 6:35:58 pm

    HEY.. that's awesome!

    Although I'd think this *should* be simpler with digital processing (e.g. why can't the NLE just detect all differences between source matte and other video channels laid on top of it??) -- that tutorial is a *GREAT* place to start playing until something simpler comes along.

    Thanks for the heads-up! (and how'd you find that?)

    ☺ Rob


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    Mike Kujbida
    Re: old tutorial for masking and duplicating composites
    on Jan 11, 2018 at 8:10:12 pm

    Rob, I'm glad you found it interesting.
    As you may have noticed, the tutorial was written for Vegas 5 so you know it's old 😀
    The author was a Sony Vegas employee. For all I know he's still working in Madison.
    I remember coming across it a very long time ago and it's one of those that got stuck in my head!
    I did a search on here for it and found that I had suggested it 12 years ago.
    Have fun with it 😁


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