What is the illusion where the contents of a 3D shape change based on which face you are looking at?

I remember coming across a Unity 3D tutorial where there was a technique where the contents of a 3D shape change based on which face you are looking at.

Say there was an hollow cube, and you are looking at the front face. This cube has a 3D dog in the middle of it, sitting down and wagging its tail. Then you go around to the face adjacent to that, and this time there is a cat sitting down in the cube.

There was a 3D game that used this technique extensively. White walls, cartoon feel, black outlines to shapes.

It also involves you walking into these shapes, and there being different rooms to explore based on which face you enter from


Any help in tracking down what this technique is called would be very helpful! I am developing a game where I plan to use it.

Thanks in advance.

 

Not sure if this has a specific name, but from what you say it's basically portals. The different destinations are at different locations, and different cameras let you look and "go through" different sides of the cube to reach the different destinations. So yeah, you should pretty much be able to replicate this with a portal approach.
A potential starting place could be this: