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two step keying and track matte in keylight issue

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Sam Cuchertwo step keying and track matte in keylight issue
by on Oct 3, 2011 at 4:00:44 pm

Hello
Thank you for the helpful techniques you've described here.
I've been getting very nice clean masks using this two step/track matte approach, but I've run into a problem that I can't figure out.
I'm trying to pre-render the masks without the background so I can add other effects and also use them in other comps but whe I pre-render them I only get a black screen. I've noticed that in my comp window, if I turn off the background layer my masked figure disappears (that is, the duplicate layer at the bottom that uses the alpha channel of the upper layer which has the keylight). What am I doing wrong?

When I pre-render I'm using Animation RGB+Alpha in my output module to preserve the alpha channel.

I really need to be able to pre-render the masks without the backgrounds

Any help on this would be really appreciated.
Sam


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ben g ungurenRe: two step keying and track matte in keylight issue
by on Oct 3, 2011 at 4:55:27 pm

It sounds like you're rendering to RGB+A, and you're getting confused because you can't really see the "A" part.... Try applying a Fill effect to your layer; it may help you see what's going on a bit easier.

I'd suggest rendering with the "Alpha Only" output module. This will generate a greyscale matte that will show where the image is cut out. You'll need to use luma mattes instead of alpha mattes, or apply the "Shift Channels" filter to the prerender and set the Alpha to the luminance channel. Also, this only renders RGB so the resulting file will probably have a smaller filesize, which makes a difference on large projects....

Ben Unguren
Motion Graphics & Editing
http://www.mostlydocumentary.com


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Sam CucherRe: two step keying and track matte in keylight issue
by on Oct 4, 2011 at 6:57:26 pm

thank you! I will give it a try.


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