Shift X
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PHONE FRAME
Finding the roll channel
Hold the phone upright and rock it side to side, like turning a steering wheel.
One to one in millimetres, from the accelerometer. Acceleration integrates twice to reach
position, and every error compounds on the way — so the integrator continuously forgets.
That is the Hold control, and it is the whole trade: long hold gives faithful
centimetres and visible creep, short hold gives a solid centre and movements that fade.
Rotation is separate and stays anchored to gravity, so the horizon never drifts.
Linear acceleration source: detecting…
How long the integrator remembers before leaking back to centre. A real 10 mm move lands around 7–8 mm here; push it to 3 s and you capture 9 mm but a residual bias of 0.02 m/s² creeps 180 mm. Nothing gives you both.
Compensates for what the leak eats. Above 100 % because a normal-speed move only survives partly — this pulls it back toward true one to one.
Soft gate: acceleration below this integrates as nothing. Raise it if the window wanders while the phone sits still; lower it if gentle movements are ignored.
Extrapolates rotation forward along the current turn rate to cancel sensor‑to‑screen delay.
Accelerometer anchors the angle, gyroscope smooths it. This is the one you ship.
Detecting…
Gravity sign: normal.