How to make shader that can show invisible items, when look through it

Unity Engine
1

How to make a window in a canvas that can peek to rendered meshes and canavases that are invisable outside that window? I currently only know of one way that allows me too do this with only meshes, but this lacks the possiblity to do the same with canvas elements:

Here is an example of what I currently made and what its limit (can hide an meshes, but not canvases):

https://www.dailymotion.com/video/x5qnj9r

2

if you want to do it with a shader i recommend asking it here (shaders) or here (image effects).

3

You are completely right! Also I already figured it out myself

I tried adding the white shader to the “material” variable of the grey canvases in the back and now they have the same effect as the boxes. THAT IS WHAT I WANTED!

Thanks for the advise.