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compositing - export in the same DPX file compositing scene and the alpha matte

Nov 13, 2013 3:48 AM

Hi guys,

you can export compositing scene  (foregrond backgrond) with  alpha  in the same dpx+alpha?

Is it possible to export in the same DPX file the compositing scene and the alpha matte?

As in photoshop.


Thank you very much


  • Currently Being Moderated
    Nov 13, 2013 9:27 AM   in reply to masamura

    Sorry, but your question is a bit confusing. 

    Are you asking if you can overwrite the original file  with two files?  I hope the answer is "no".


    Are you asking if AE can create a second file of just the matte?  Yes: You can set AE to render Alpha Only and it will create a standard black-and-white matte.

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    Nov 14, 2013 2:42 PM   in reply to masamura

    Yes: this is done all the time in AE.  Simply add your background layer to the AE composition with the chroma key footage.  Then render a new DPX sequence.  Very simple.

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    Nov 15, 2013 8:04 AM   in reply to masamura

    You will need three DPX sequences:

    1. The subject on green screen
    2. A matte for the subject
    3. The background


    You have the subject and the background.  You need the matte.  You can make one in AE by keying the subject, then rendering the alpha channel only.  You will then create your matte.  And if you want ONE DPX SEQUENCE ONLY, you will have to take all three and put them end to end, creating one long DPX sequence.  There isn't a way to create a single file that will do all things, as it seems that you hope AE will do.


    After color correction, you may have to bring the color-corrected sequences back into AE for final compositing.  In AE, you can add Light Wrap, a process that helps you incorporate the edges of the subject into the background, and you avoid the look of a television weatherman in front of a weather map.


    Or, since you've used Nuke before, you can use it again in a workflow that seems to be more comfortable for you.

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    Nov 15, 2013 10:26 AM   in reply to masamura

    AE can only generate an alpha channel from transparent areas inside the comp. There is no channel rendering based on layers. This does sound like a great idea for a plug-in though. Developers, are you listening???


    A workaround would be to pre-compose your keyed footage and render both the composite and the pre-comp. That's what I have done in the past for color correction. The colorist just loads up both clips so the matte can be used to separate the layers for color grading.

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    Nov 15, 2013 11:14 AM   in reply to masamura

    As far as I know, DPX doesn't support multiple layers. OpenEXR serves that purpose. So as to be able to export multilayer OpenEXR from AE, you need ProEXR plug-in from fnord.

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    Nov 20, 2013 1:59 PM   in reply to masamura

    I think you can do this in AE.


    1. Make a new comp that has your final scene as the layer.

    2. Drop in your alpha as a new layer and set it to be the first layer's alpha/luma matte.

    3. Render to DPX with alpha, alpha interpreted as straight.


    This should give you a DPX with the full image in RGB and your alpha in place. To check the output, import the rendered files back in the AE and interpret with alpha ignored and you should see the comped scene.

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