Vuforia: How to make an object appear out of thin air?

It is very similar to this question, however I don’t have an image target. I just want the object to come out of an invisible wall, make it appear out of thin air. Like an Augmented Reality portal, but the portal is closed so you can’t see inside the portal, and the object comes through the portal.

I attached the depth material to a cube and enveloped my object with that cube. Done.