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How do I create a foreground matte?

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Saturnv5
How do I create a foreground matte?
on Jun 24, 2005 at 4:15:25 am

Hi there,

I have been experimenting with the foreground matte feature with Twixtor 4.5 Pro. It works great, but I'm sure there's a better solution than to just trace each frame of the video than making a white mask against a black background.
Also, when I set the inverse mask to anything above zero, I can clearly see where Twixtor attempted to fill in the gaps, is this normal?

Thanks in advance :)

David


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Pierre Jasmin
Re: How do I create a foreground matte?
on Jun 24, 2005 at 10:08:52 pm



for your second question play with the Invert Shrink Matte (does that help?)
If not, we just fix this problem in Shake and Discreet systems, so there should be an update for you soon I guess.

Pierre
http://www.revisionfx.com


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saturnv5
Re: How do I create a foreground matte?
on Jun 25, 2005 at 12:46:45 am

Thanks, infortunately I use Adobe After Effects.


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saturnv5
Re: How do I create a foreground matte?
on Jun 25, 2005 at 12:46:50 am

Thanks, unfortunately I use Adobe After Effects.


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Pierre Jasmin
Re: How do I create a foreground matte?
on Jun 26, 2005 at 12:19:54 am


The problem I discussed would typically happen only with very large values, if you set FG1 Inv Matte Shrink to 0.75 or 1.0 does it help?

Pierre


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saturnv5
Re: How do I create a foreground matte?
on Jun 27, 2005 at 5:51:49 am

Yes, if I set the inv mask value low (eg 0.5-1.0), it looks fine, thanks. However, if the background is complicated eg the inside of my bedroom :(, Twixtor can't seem to guess the background very well.

Does anyone know the answer to my first question.

Thanks David :)


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Pierre Jasmin
Re: How do I create a foreground matte?
on Jun 27, 2005 at 9:41:08 pm


It's mainly an issue if you have a foreground object close to the camera (like someone jumping on your bed) and you follow that person with an hand held camera. In this case with the "proper" camera motion you can create a situation where a large chunk of the image is revealed at a new frame (occlusions). For such case as well more frames per second can help (that is would probably work better from 59.94 then 24P). As well if you are in control of shoot, perhaps try to move the camera slowly and have the actors sort of play their part in slow-mo if possible. In the end it's all about how much something moves in pixels per frame, so often times, to capture someone jumping on your bed looking at them from the front as opposed to the side will produce better results.

I am not sure which is faster, to clean your bedroom or to do roto... Seriously, you can use tracking points (the Point Positions) or roto shapes to first help the background registration and make sure that is perfect. Once you add geometry guidance then crank up sensitivity to 100%. If the lighting is low, as is often the case with interior shots, try the Image Prep (edge-contrast) setup. Geometry is animatable (on-off) so you can limit your intervention for that to only the frames and within frames to the frame areas that are bad (read the doc for details). If you have frame edge artefacts, you can try Inverse /Smart Blend mode for Warping.

Pierre
http://www.revisionfx.com


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saturnv5
Re: How do I create a foreground matte?
on Jun 29, 2005 at 4:31:09 am

THanks alot for the advise


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