How did we determin that the space we occupy is actually 3d and not just 2d disguising itself as 3d?

I’m imagining a videogame or a painting (possibly a simulation) with good enough graphics/detail/input/sound design to the point where the brain only registers the sensation of space, interprets distances and makes the assumption that things have ”sides” (even though you can only ever see one side of anything) because we’re presented with a high enough amount of definition and realistic features/inputs in relation to what we expect of 3d. You think something has sides because manipulating it changes the way it looks, but what if thats only generated upon manipulation?