Mario 64 was the proof of the strengths of the N64. More than that: Mario was the explanation for the N64 having been made the way it was. It was hardware and software in unison; it explained the analogue stick and C buttons, in hindsight almost absurdly tailored to that one game.
Unfortunately, Nintendo couldn't repeat the same trick. The 3DS’s defining hardware characteristic came with a switch to turn it off and a warning that children shouldn't use it. So Mario had to work without it.
However, 3D Land did expose some ways game makers could play with 3D, even if it couldn’t commit to them itself. There was the fact that parts of the game were actually a throwback to isometric 3D of the 1980s (Populous, Zaxxon, Snake Rattle ’n’ Roll, etc.). A delightful joke: build a 3D environment, render it from a fixed angle, with mis-sized, off-grid blocks, then only communicate depth with the stereo images. It’s a funny leveraging of the brain-hack approach to 3D of a stereoscopic display. Your brain is able to decode what you're seeing even though it would never be encountered in the natural world.
You’re really seeing a new world, which is mindblowing (if you switch it on).
Holding a window versus holding a projector
But there was one other idea that 3D Land showed us, even though it didn’t make use of it itself. That was the ability, with the d-pad, to toggle the 3D type between innie and outie: keep all the depth behind the screen, or allow it to stick out in front.
This option shows us two different models of how a 3D world can stand in relation to a viewer: one like holding a window; one like holding a projector. The window has the world behind it, the projector has the world in front of it.
Interestingly, though, the window can be made sense of in the topology of the game world whereas the projector cannot. What’s the nature of this new world we’re seeing?
In my diagram, a set of three red balls is presented to a viewer in three different ways. In the 2D example, each eye sees the same parts of the scene exactly. In the “window” and “projection” examples, the frame of the screen obscures a different part of the scene for each eye. The yellow shaded area shows where both eyes can see and where the scene will resolve cleanly in three apparent dimensions. Outside that area, only one eye can see the scene, the other being limited by the edge of the screen.
The “window” diagram could equally represent three red balls outside an actual window. The principles of the diagram would be the same. It’s impossible for the right eye to turn and see the right edge of the right ball because the right edge of the window frame is in the way. You would have to move your head or the window frame and have a look round the corner. (This is the 3DS tech’s biggest ask for suspension of disbelief: you can’t look round the corner. That’s a major differentiator for VR, and the part that makes you sick if the latency is bad.)
The “projection” diagram, on the other hand, could not in the same way be used to represent three balls in front of a window. Here the right eye cannot angle itself to see the left edge of the left ball because the left edge of the frame is “in the way” – even though it’s behind it. The window frame would to obstruct your line of sight to the ball even though the ball is in front. The pretence of 3D here is completely impossible in the natural world. The projected scene and the real world cannot stand in relation to one another insofar as the boundaries of the screen are crossed and the scene extends outside the sweet spot where both eyes can see.
Is one of these better? Apart from one sticking out and the other sticking in? Perhaps you would feel like the window version, since it presents a consistency between your universe and Mario’s, places you in the game world in some way. Perhaps, on the contrary, you would feel that the window ties the game world to mundanity in a way that is destructive of its fantasy – a little toy world in your magic box. In that case it is rather the projection that allows the imaginative leap into the game world.
Of course the correct answer is that neither is absolutely better. However, if you had a game which involved holding a window into another world, then that would be depicted very nicely by the window model.
Likewise, although the projection model doesn't make sense in some very strict interpretation, its basic idea is that stuff sticks out of the screen. That could of course be used to depict some relevant scenario of holding a sticky-out thing between your hands (a Doki Doki Majo Shinpan! update?), although the depiction will be contravened if that thing crosses the boundaries of the screen and introduces the impossible aspects of the illusion.
One last possibility for the projection model: it actually depicts something you cannot experience in the real world – the visual presence of two worlds that cannot logically relate to one another. These are the game world and our world – ours represented by the frame of the 3DS. The only point these two worlds can have in common is the viewer, who sees them both.
Seeing a universe isolated from our own sounds like a science fiction scenario. Imagine a sci-fi game that portrayed that with visuals only possible on a 3D screen. Now that would be hardware and software working in unison.