adobe illustrator - How to hide what's behind an object in a non destructive way / give it an "invisibility cloak"

is there a way to design a linked graphic in Illustrator with some kind of invisibility cloak in the layers.

Let me explain. Let's say I want to reuse a sketch like this

Where in fact, the rectangle fill color is transparent, and I don't really want to have a purple fill color for the ellipse, but I want it to hide the path of the rectangle.

Then, I want to be able to reuse it on some backgrounds like this:

In order to reach the final result

The thing is: I don't want the ellipse to really be purple in the image that I save in my Illustrator Cloud library, I just want it to adapt its color to whatever is beneath the rectangle layer

That way, if I have an orange background, I want to immediately (without modification of the link) reach the following result

instead of this (my current achievement)

Is it possible without embedding the image nor destroying the shapes? Really, as if the ellipse was acting as an invisibility cloak for the rectangle.

Answer

Use knockout groups. The benefit being that knockout groups is that you can not just hide pained areas you can also partially hide things, and you get to affect exactly how deep in the stack the effect knocks out and whether it knocks out fill or stroke or BOTH. It is also usable inside effects which makes it far more flexible than shaper.

To use knockout groups you need two things

1. a group marked as knockout in the transparency panel.


2. any transparency applied in that group now eats out of the group. So if set a fill 100% transparent then you get the effect you described.