Only render inside a volume?

How can I have actors only render inside a particular volume? I do not mean just turning off the Actor if it leaves the volume. As they enter or leave, the geometry inside the volume needs to be seen, and the geometry outside should be hidden, culled/clipped, or made transparent in some way. A soft fade would be nice, but just a hard clipping would do, too. It’d be awesome if the cut face got filled in, so I don’t see the insides of my model, but I’m guessing that that’s really hard.

Suggestions welcome!

Hey man, did you ever find a solution for this?

Use a boxmask on a masked material i think would work.