POVRay doesn't show object behind difference

I have a POVRayfile which creates this cone using Mesh2:

and I would like to cut a piece out of it, so I can see inside. For this I'm using an intersection with these 3 boxes:

union {
    box {    <0,0,0>     <-100,-100,100>
        texture {
            pigment {
            color
            <1,0,0> 
            } 
        } 
    }
    box {<0,0,0>        <100,-100,100>
        texture {
            pigment {
            color
            <1,0,0> 
            } 
        } 
    }
    box { <0,0,0>        <-100,100,100>
            texture {
            pigment {
            color
            <1,0,0> 
            } 
        } 
    } 
} 

which then looks like this (file):

The part I wanted to get rid of is "gone", but it's not transparent. How do I make POV-Ray look into the cone?

Intersections are not meant for this. They are designed to cut into a solid body (and thus create a new surface).

You have to use the "clipped_by" property. More details here:

link