How to composite 2 images together FCPX or Motion?

Discussion in 'Digital Video' started by Freida, Dec 12, 2012.

  1. macrumors 6502a

    Oct 22, 2010
    Hello guys,

    I have a question for you if you could help me please I would highly appreciate it.

    I have 2 images - 1 is a animation render with alpha channel and the other is just a background. All I want is to be able to have the character in the front and put the background behind it but I don't know how to do it. When I try to put it in the background it kinda ignores where the alpha is and it looks like just two pictures on top of each other.
    What am I doing wrong? I want the place where there is no alpha to be transparent so the background is visible there. As its gonna be image sequence, is it better to use motion or final cut or it doesn't really matter?

    Thank you very much for any help
  2. thread starter macrumors 6502a

    Oct 22, 2010
    no suggestions, please?
  3. macrumors newbie

    May 29, 2012
    Both FCPX and Motion can composite layers with Alpha channels, but only Motion can easily create an alpha channel. But, from the sounds of it, your alpha channel should have already been created when you exported your animation. Are you sure the animation has an alpha channel? If it does, FCPX will see it and automatically composite the image.

    What software are you exporting the animation from? What are your export settings? It should be in a format that is compatible with Alpha channels such as Quicktime ProRes or Animation. A format such as Quicktime H264 will not carry an alpha channel.
  4. thread starter macrumors 6502a

    Oct 22, 2010
    I haven't got to the stage to have a whole sequence as I'm still tweaking the render. What I did was to save the render image as psd and imported it to final cut. Then wanted to put background behind the character but I just don't know how to do it in final cut as they both seem to be on top of each other. I have checked the image in photoshop and it does have correct alpha so I'm not sure what am I doing wrong.
  5. thread starter macrumors 6502a

    Oct 22, 2010
    ok, found the issue. PSD format doesn't work. Saved it as Targa and now it works fine. One issue though. How do I get rid off the ugly outline around the character and props, please?
  6. macrumors newbie

    May 29, 2012
    If the background of the alpha channel image is anything other than black, you will get an ugly outline.
  7. thread starter macrumors 6502a

    Oct 22, 2010
    Ok, thanks. Yeah, managed to fix it with another layer :)))
  8. macrumors 6502

    Nov 28, 2011
    Stuttgart, Germany
    That works, yes. You can also play around with the Composite mode, which will give you some interesting effects. Especially if you are compositing explosions or other things with mainly light (or bright areas) in them. In FCPX, mark your top clip and open the Inspector (Cmd+4). At the very bottom, you will find not only the Opacity slider, but above it the composition mode. There is a plethora of options and going into all of them would get out of hand. But it helps to know that there are some interesting effects there to compose two images.

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