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Creating a Mask That Affects All Layers Below

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James Gordon
Creating a Mask That Affects All Layers Below
on Oct 15, 2014 at 9:12:17 pm

I'm creating some projection mapping content in After Effects. The building wall I'll be projecting on to has several windows that I don't want anything to shine into from the projector.

I've created a black and white psd file of the wall with the windows black and the rest of the wall white.

Is it possible to use this B&W image as a top layer matte in order to mask out the window area of all the content layers and comps I place below it?

I've tried a luma track matte which worked but only affects the layer immediately below it.

As I type this I just got the idea that maybe the simplest thing to do is to create a psd top layer that just has black where the windows are and is transparent everywhere else (instead of white).

Still curious though about the possibility of a top level matte that affects all below it. Thank you.

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Roland R. Kahlenberg
Re: Creating a Mask That Affects All Layers Below
on Oct 16, 2014 at 11:36:05 am

The mask or layer with the 'master' Alpha Channel should be placed at the very top of the layer stack - then set its Blending Mode to Stencil Alpha.

- Roland

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James Gordon
Re: Creating a Mask That Affects All Layers Below
on Oct 17, 2014 at 5:43:15 pm

thank you so much Roland!

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