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Forums Adobe After Effects make mask from alpha

  • make mask from alpha

  • benito sanz

    April 16, 2005 at 12:32 am

    hi all!

    just been checking the after effects help file to generate a mask from alpha channels. i have a series of stills, a sequence of images actually, all of them have had the background removed in photoshop but the result wasn’t very good ,all the edges are jaggy. i have used autotres to generate the mask from the alpha, it works fine but i can’t apply mask expansion nor feather, i’ve converted all the keyframes to liner just to see if that way it would work but nothing.

    can anyone tell me if it is posible to apply the expansion or feather please, the manual doesn’t actually say anything.

    thank you very much.

  • Chris Smith

    April 16, 2005 at 12:48 am

    If you use the auto trace in AE, it will probably create a lot of masks. You will have to set the feather and expansion on each one.

    Chris Smith
    https://www.sugarfilmproduction.com

  • benito sanz

    April 16, 2005 at 1:01 am

    thanks chris, it doesn’t seem to be working, anyway i will do the mask and animate it again,

    thank a lot

  • Steve Roberts

    April 16, 2005 at 1:02 am

    … but if you don’t mind expressions, you can pickwhip those properties on all masks (except Mask 1) to those properties on Mask 1.

    1. Select Mask 1 & 2, hit MM to reveal mask properties.
    2. Alt-click on the stopwatch for Mask 2’s Feather property, and pickwhip it to Mask 1’s Feather property.
    3. Do the same for Mask 2’s Expansion Property.
    4. Select Mask 2’s Feather Property, and its Expansion Property and select edit>copy expression only.
    5. Select all the other masks (3 and onward), and select edit>paste. That pastes the two expressions to the other masks.
    6. To adjust those properties for all masks, adjust them for Mask 1.

    Hope that helps,
    Steve

  • Chris Smith

    April 16, 2005 at 1:06 am

    Steve,

    Because I’ve been learning C4D all week, my head is cloudy: Is there not a away in AE to merge the masks in some fashion? Kind of like boolean operations in 3D.

    Chris Smith
    https://www.sugarfilmproduction.com

  • Nicholas White

    April 16, 2005 at 1:22 am

    Hey,

    Have you considered opening the files in Photoshop, selecting the alpha channels, then applying something like a gaussian blur to them, effectively softening the edges? If you make an action of it, you can run it as a batch on your files and have them done while you’re making lunch or something 🙂

    Take care,

    Nick

  • Steve Roberts

    April 16, 2005 at 1:32 am

    As far I know, the (Boolean) mask modes only work when masks overlap, and that only affects how they reveal the layer. They still act independently when it comes to mask properties.

    That said … maybe the masks could be pasted into Illustrator, then a Pathfinder action done on them. But for animated masks, that could be problematic.

    Steve

  • Chris Smith

    April 16, 2005 at 5:41 am

    Nick,

    WHy go through the hassle of running it through PS? Just blur the footage. Precomp the layer then do the auto trace.

    Steve,

    Yeah, Pathfinder type actions is what I was thinking would be great in AE. Especially to deal with the auto-trace creating so many masks. Or an auto trace option to combine the masks ala Pathfinder.

    Chris Smith
    https://www.sugarfilmproduction.com

  • Nicholas White

    April 16, 2005 at 6:15 am

    Chris,

    I had a similar problem this week and resolved it by running my files through PS. Lord knows I’m not too savvy with masking in AE and it seemed relatively easy (and got the job done the way I wanted to); I hadn’t thought of doing it the ways you and Steve had mentioned…how many ways are there to skin a cat? : )

    But, believe me, I’m reading this post attentively to learn a lot more about ways of doing projects like this in the future without resorting to exporting to PS.

    Take care,

    Nick

  • Chris Smith

    April 16, 2005 at 6:54 am

    I can dig it. Usually ppl only bother batching through PS when it is something unique to PS. Obviously Gauss blur is in AE so you need look no further. You just probably have to pre-comp the layer after adding blur so the auto trace will read it as a complete rasterized image with the blur on it.

    Chris Smith
    https://www.sugarfilmproduction.com

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