Making a layer visible only when viewed through a mask

Hello everyone,

I'm new to the whole shader thing, and I was wondering if someone could offer some assistance. I'm trying to make it to where, as the title says, a layer in my game is only visible when viewed through a mesh. Kind of like a reverse mask, or a portal. I don't have Unity pro, so I'm trying to figure out how to do this without using render textures or stencil buffers. I found a shader for a regular mask, but I can't figure out how to create an inverted mask, and after countless days of searching the web and browsing the forums, I've decided to give up and come to you guys. So, if it isn't too much trouble, could someone help point me in the right direction? Like I said, I'm new to this, so see if you can find a simple example.

Thank you!

 

You can use a depthmask shader on a mesh, along with two cameras, where the second camera displays only the desired layer.

--Eric

 

Thanks, it worked!!

In case you're wondering what I'm working on, a screenshot: