Create a mask based off of a key

[Greg Gesch]

Hi. What exactly are you trying to do – why make a mask?

[Billy Rodgeers]

It’s entirely hypothetical, but if I would want to easily make a mask around something, it would be much easier just to do it based off a color selection right?

[Andrew Somers]

Animated masks are the realm of MOCHA. It’s not uncommon to use Mocha for masks even when doing green screen.

But, do you specifically need a mask for something and you can’t use the alpha channel?

Andrew Somers
VFX & Title Supervisor
https://www.GeneralTitles.com

[Billy Rodgeers]

No, I think you’ve answered my question. Thanks

[Steve Bentley]

Don’t forget you can follow a track with and move, rotate, whatever another turned off version of your keying layer – in effect it becomes and independent “mask”.

[Roei Tzoref]

there’s also layer-auto trace. you can create a mask based on alpha.
https://helpx.adobe.com/il_he/after-effects/using/creating-shapes-masks.html#create_a_mask_from_channel_values_with_auto_trace

Roei Tzoref
2D/VFX Generalist & Instructor
♫ AeBlues Tutorials ♫
http://www.tzoref.com