Seeing the room through a headset is only the first part of mixed reality. The more interesting part begins when the application has a reason to care where the walls, furniture and people are.
Meta's Presence Platform and its The World Beyond demonstration put that relationship in focus. The platform brings together capabilities for mixed-reality experiences and interaction. The demonstration gives those capabilities a setting in which the surrounding room contributes to what happens.
A camera image alone does not provide the same information as a room model. It can show a table to the user while leaving the application with no usable idea of its shape or location. To place a virtual object convincingly, the software needs a spatial relationship that remains stable as the user moves.
There is a useful progression here. First, an object appears over the view. Then it is anchored to a location. Then it can respond to surfaces, pass behind things or participate in an interaction that uses the room. Each step adds obligations as well as possibilities.
A playful creature is a good example. If it stands on a floor, it needs a plausible contact point. If it hides behind furniture, visibility must agree with the furniture. If the player reaches toward it, the interaction must have a clear target and response. A convincing result depends on those small agreements.
The room also varies between users. A scene designed around a large empty space may fail in a crowded one. The software should have a way to adapt the experience, offer a smaller version, or explain what space is required. The user's home is not a standardized level supplied by the developer.
I think this makes restraint valuable. One interaction that fits the room can feel more convincing than a large set of effects that ignore it. A virtual object with a stable location, understandable behavior and a clear response to the user's hand has a strong foundation.
Persistent placement introduces a further question: what happens when the physical room changes? A chair can move. A table can be cleared. A previously suitable location can become obstructed. Remembering a coordinate is not enough if the application assumes that coordinate still describes the same environment.
For me, mixed reality becomes interesting when the environment changes the design. The application should use the room's structure to create a particular experience, while remaining honest about what it can sense. Passthrough gives access to a view. The work after that is making the relationship between the view, the model and the interaction coherent.