Hi Jim,

I doubt it would be possible to do with the hidden mesh.
If you want to do this for AR Unreal scene, then this might work: https://my.aximmetry.com/post/1960-ar-pop-out-effect

Warmest regards,

And in non AR mode?

is there a shader to make a mesh a garbage mask? (Not included in rendering but making sure video does not get displayed).

It'd take some R&D but you have 2 options. In UE there are options for occlusion of objects and collision detection. With some research you could probably achieve what you want with a one of these methods.

The other option is a 3D object for matting inside of Aximmetry itself. The virtual cam setup has a version of this for matting out the walls of a greenscreen studio so there's no reason you couldnt do something similar with your own 3D object as long as it was in the same 3D space.