It would work like Unity’s masks, hiding parts of the objects under it (only objects that have Masked automatism would be affected). Example how it would look like (obviously Unity here): forum.unity3d.com/attachments/example-jpg.53012/ (wasn’t able to find better picture, but that how it would work).
You’d just load grayscale image to be used as mask and it would mask objects under it that has Masked automatism.