Inverse Depth Mask?

How would it be possible to create an inverse depth mask? In this case, I refer to a depth mask as a shader attached to a mesh that ‘pokes a hole’ through the current camera layer to let you see the camera render layer one depth down, usually by using ColorMask 0.

What I want is for, instead, the mesh to determine what ISN’T cut out, without everything that is NOT seen through the mesh being cut out.

It sounds like “ZTest Greater” is the thing that you’re looking for, i.e. reverse ZTest in a shader.

Unity 5.0 UI Reverse Mask