From this Wired story, link found in another post above https://www.wired.com/story/google-project-starline, there is this passage: Move to the side just a few inches and the illusion of volume disappears. Suddenly you’re looking at a 2D version of your video chat partner again.
This implies, AFAIK, that it either uses lenticular lenses (which is the tech 3D-cards typically use), or a parallax barrier (screen tech from 3DS). There are a thus sectors from the screen to the viewer, and you need to have your head placed so that your one eye sees one sector, and the other eye sees another. What the reporter describes is when both her eyes end up in the same sector, which immediately makes the result 2D. Note that there might be more than two sectors, so that you can move further sideways and get a realistic view, but each eye must all the time be in a different sector. It can also use head tracking to achieve such correction of your view wrt. movement of your head, since it evidently constructs a full 3D scene of you and the other side, it can render that from any angle.
This implies, AFAIK, that it either uses lenticular lenses (which is the tech 3D-cards typically use), or a parallax barrier (screen tech from 3DS). There are a thus sectors from the screen to the viewer, and you need to have your head placed so that your one eye sees one sector, and the other eye sees another. What the reporter describes is when both her eyes end up in the same sector, which immediately makes the result 2D. Note that there might be more than two sectors, so that you can move further sideways and get a realistic view, but each eye must all the time be in a different sector. It can also use head tracking to achieve such correction of your view wrt. movement of your head, since it evidently constructs a full 3D scene of you and the other side, it can render that from any angle.