How did Duck Hunt for the NES know where you were pointing the gun?
In: 7118
The gun in the NES used by duck hunt was a civilian/consumer implementation of the revolutionary innovation known as a “[light pen](https://en.wikipedia.org/wiki/Light_pen)” which was initially developed by IBM for the [SAGE air defense system](https://en.wikipedia.org/wiki/Semi-Automatic_Ground_Environment) in the late 1950s, allowing radar operators to point to a spot on the screen and identify a specific radar target (SAGE only lasted a few years before NORAD went into service, but its a fascinating internet rabbit hole to go down if you’re interested in tech, as a number of innovations eventually made their way into consumer hands decades later – a single one of the 30 blockhouses was equivalent in performance to an 80286 computer, which was *insane* in 1958)
Because the computer is generating the image, it knows where in the scan process the electron beam in the display is at any given moment, the gun/pen is focused on a small area of the screen, pulling the trigger switch tells the computer exactly what part of the screen it’s aimed at, because the spot the beam is at is significantly brighter, relying on the phosphor to keep the image visible until the next pass of the beam, 1/29.97th of a second later. If the requisite pulses are all lined up with the software/ROM logic, that then correlates to an object (such as a duck, or an incoming Soviet aircraft) additional processing is then triggered. Otherwise it registers as a miss.
Because modern LCD displays don’t use a scanning electron beam to make the image, this approach no longer works, which is why you can’t play Duck Hunt on a modern TV/display.
Latest Answers