What's the potential of turning this privacy hack into a 3d one by use of specialized display driver and polarized glasses?
From what I understand, LCD monitors have two sets of polarized filters. One can have it's polarity rotated electrically and the other one is fixed. If the rotation angle required for going from bright to near black is small enough and if the liquid crystals are capable of a large enough angle, then the extremes of the maximum angle could be used for the images sent to both eyes.
If the maximum angle is small or the fade angle is large, then that reduces the number of usable colours, or worse, gives inverted image for each eye.