Now if you’re in the chair and the chair tilts back 30 degrees then yes, your view should tilt up 30 degrees but attached the platform is another gyrometer/accelerometer, from the same company that makes the ones in the rift.
The two gyroscopes effectively cancel each other out.
This gyroscope/accelerometer registers a 30 degree shift in motion in one axis, the Rift gyroscope/accelerometer registers the same movement because your whole body, including the Rift on your face has rolled backwards by 30 degrees even though your face is facing the same direction.
Now, whenever the chair moves, we register the rotation of the chair and the rotation of the Rift, in 3 axis’ about 1000 times a second. We then subtract the rotation of the chair from the rotation of the Rift and this value is what is used by the game to determine where you are looking. So the 30 degrees movement example above returns a zero rotation. 30 – 30 = 0. Your body has rotated backwards but you’re still looking directly forward.
Now you’re tilted back 30 degrees and you look up, 10 degrees. The Rift gyrometer registers a 40 degree rotation, but because the chair registers 30 degrees, you have a 10 degree difference.
The oculus rift camera is also attached to the sphere so it moves with you.
40 – 30 = 10.