Don’t we need up/down, left/right, forward/back?

They would be nice, but perhaps we can simulate them cheaply instead.

Close your eyes on the highway (not while driving please! :p) and you receive very little motion input, even if you’re travelling at 200mph! You will feel the roads surface via tactile vibrations but they don’t tell you how fast you’re going. All you can really feel is the normal pull of earths gravity of 1g pulling you into your seat.

Now if the driver puts on the brakes your body will continue to move forward and the mass creates a second g force. You are pushed forward. From a stop if you accelerate in a fast car you will be pushed back into your seat.

Now if you sit on a rocking chair and someone pulls it back when you’re accelerating in a computer game, if you can’t see the reality because your eyes are covered by a head mounted display, you’ll interpret this as moving forward since this fits in with your experience. Your eyes and inner ear agree that you’re moving forward, so you ‘are’.

The same applies with sway, or side movements. Roll to the side and your eyes, helped with gravity pulling on your inner ear, will tell you you’re moving to the side.

So we can fool 2 of the translation movements with rotation, what about heave, or up or down movements?

This is a little trickier, ahem, make that impossible. To feel like you’re going up or down you really have to go up and down. We’re not that easily fooled, however we do have a major advantage that we can use to help us. We’re basically only five degrees of freedom animals anyway.

Most of the time we walk about in 2D space, we even drive in 2D, we go northsoutheastwest but never really up or down. To feel heave in a car you need to go over a hump back bridge pretty quickly.

Even while flying a plane you’d be lucky to experience more or less than 1.2g in a normal flight. Did you know they rolled the concord aeroplane keeping positive G? Jump to 2m 50seconds.

They probably could have done it with passengers and they wouldn’t have noticed

The other advantage I can claim is that I’m making a motion simulator for use in space games where were can assume we have artificial gravity, and once the pitching and rolling has stopped, down will always be down.

So, most people would be happy, except possibly pilots who know what +1g or -g really feel like. Chances are they already have a decent sim (or plane) and don’t want a cheap simulator.