If you’ve ever played Duck Hunt or any of the other NES games that used the NES Zapper gun, you probably at one point or another wondered how the game actually knows where on the TV you are aiming the gun when you pulled the trigger. It turns out, the method for accomplishing this is incredibly simple, as is the gun itself.
This gun primarily just consists of a button (the trigger) and a photodiode (light sensor). When you pull the trigger, this causes the game to make the TV screen go completely black for one frame. At this point, the game uses the light sensor to sample the black color it’s reading from your TV to give it a reference point; this is essential given that the ambient light in a particular room and other things of this nature can vary greatly. In the next frame, the game causes the target area to turn white, with the rest remaining black. If the game detects a shift from black to white from the gun’s photodiode in that split second, it knows you were aiming correctly at the target and so doesn’t specifically need to know anything about where on the screen the target is.
For games with multiple targets at any given time, the same type of method is used except multiple target frames are shown. So the game will flash the black reference screen; then will flash one of the targets, leaving the rest of the screen black; then flashes the next target, again leaving the rest of the screen black; and so on. The game knows which target is hit, if any, by which frame is currently being shown when a light shift is detected.
more here
good read, always wondered how that work.
This gun primarily just consists of a button (the trigger) and a photodiode (light sensor). When you pull the trigger, this causes the game to make the TV screen go completely black for one frame. At this point, the game uses the light sensor to sample the black color it’s reading from your TV to give it a reference point; this is essential given that the ambient light in a particular room and other things of this nature can vary greatly. In the next frame, the game causes the target area to turn white, with the rest remaining black. If the game detects a shift from black to white from the gun’s photodiode in that split second, it knows you were aiming correctly at the target and so doesn’t specifically need to know anything about where on the screen the target is.
For games with multiple targets at any given time, the same type of method is used except multiple target frames are shown. So the game will flash the black reference screen; then will flash one of the targets, leaving the rest of the screen black; then flashes the next target, again leaving the rest of the screen black; and so on. The game knows which target is hit, if any, by which frame is currently being shown when a light shift is detected.
more here
good read, always wondered how that work.