Shader Clip with Stencil

I'm really new into shader programming, I got the concept of Stencil and Clip(), what I'm trying to make is a shader which gets "clipped" if an object collide with it, like in this example:

https://www.youtube.com/watch?v=iHV6F8DM63o

But I want it to clip based on the object's geometry and not just position, like a Stencil. How can I get the geometry of the shader and make the comparison for the Clip(). ?