Raaaid...
I´m going to ask you to do one little experiment. So, please, try this:
Run the sim, if possible in a wide screen. Close one of your eyes and try to fit the visual screen to cover all you visual field, or at least, as much as you can while capable of focus the image. Also try to center your non stereoscopic point of view in the center of the image.
Then, with track Ir or mouse, start moving a bit the point of view. Better if you displace the view plus rotate it. Try this for a few seconds and then tell me what do you see.
There are various ways to feel deph and stereoscopic is not the only one. Real stereoscopy is the only way to feel realistic deph when no other information is provided or memoriced by the brain. But the 3D feel is in fact created by the brain, and the brain can recreate it with only one source image IF it have all the other neccesary information to do that. In this case that information become from image movement and your previous knowledge of the cockpit and how the perspective works ( the brain "know" all this ). So the brain can reconstruct the sense of deeph. And doing this you can feel the 3D even without seeing double the objects that are out of focus. I know not every people can see this effect with only one eye, but I see it as well as I do crossing the eyes with two images. BUT is a fake sense of deph and if you try to play ( or drive a car ) that way you are going to miss a lot of targets ( or hitting a lot of other cars ) because bad calculations. Is like the brain filling the dead spot of our vision. Appears to be real, but is not. If you put some small object in that spot, that object will vanish completely.
Now, when we are talking about real deph feeling builded by the brain trough two images, the sense of scale becomes certainly from eyes separation and image sizes as I posted before in this threat. Where I used to work we had a cave ( I´m a 3d modeler and I was modeling 3d enviroments for that thing ), wich is a big cube where all faces are screens and where you enter with a steresocopic glasses and a fully head tracking. In the screens you project sterescopic images calculated from your actual point of view inside the cube. This way, with the correct space between eyes rendering, and the fully size and scale of the image, the sense of being there is absolutely real and fully credible. It´s an amazing experience. I literally could enter and walk my 3d enviroments and after a while you can forguet that was only a fake image and tryed to touch everything and avoid colision with objects.
The problem with 3D video games or cinema is that they lack the possibility of project a fully realistic scale image from the point of view of the user, so you get weird 3D effects, usualy exaggerated. Otherway raaid, the sensation is fully real and no different in ANY WAY from the real thing.
Edit:
I have found a cave photo in google, I post just as curiosity. The one I worked on was very similar to this:
