Obtain alpha values from custom stencil

Development Rendering
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1

Hi! I’m trying to isolate a character from their background with postprocessing. This is my current blueprint for my postprocess material:

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image906×508 101 KB

Here is what the result looks like:

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image1014×896 33.9 KB

The hair regions don’t look good, and I’m trying to find a way to get the translucency/alpha values of the character from the custom stencil. It looks like my custom stencil currently only tells whether or not something is part of the stencil, and not anything in between. For example, since the hair regions are more translucent, I would like the custom stencil to output a value between 0 and 1 to blend those regions better. Is there a way to do this?

I’ve tried enabling alpha channel support in post processing in the project settings, but that doesn’t seem to change anything.
I’m on UE 4.27.2

2

If I am not wrong custom stencil values are the same in all channels, meaning that it doesn’t matter which channel you choose. I didn’t work with custom stencil that much, but I think you would need another node such as sceneTextureOpacity

3

Anti-aliasing may also be a factor. Be sure to set your post process to before tonemapping to ensure that it receives AA which will hopefully improve the hair but also probably get rid of the jagged aliasing along the side of the face and ear.