It came out nearly 40 years ago. They didn’t put out “real” motion sensing games until 2006. Feels like I’m missing something.
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The “gun” is just a light sensor with a lens on it to narrow its field of view into a narrow beam. When you point it at the television the sensor will only see a small part of the screen.
The trick is that when you press the trigger the screen will momentarily stop displaying all the normal graphics of the game. Instead it will only show a black screen with a white square around where the target duck (or dog) is. If the light sensor detects light then it assumes you were pointing the gun at the right patch of the screen and triggers a hit. If no light is detected you were presumably pointing at the wrong part of the screen and no hit is triggered.
Of course such a simple system could be fooled by pointing the gun at a light bulb and you would get hits every time. (Edit: Correction, there was a system to prevent this by displaying a black frame first. Thanks for the info /u/The_Thunder_Child and /u/ToxiClay !)
The game didn’t sense motion at all.
Inside the Zapper is something called a *photodiode* — an electrical device that generates an electrical signal when light falls on it.
If you pay really close attention to the game when you fire the Zapper, it goes black for a single frame, then draws white boxes around the ducks for another frame. (For multiple ducks, the white boxes persist for different durations to allow for differentiation.)
If the Zapper sees a frame of no light followed by a frame (or more) of light, you must have been aiming at the duck, and so the game scores a hit. If not, then you weren’t — no hit.
So what happened when you pulled the trigger on the gun was that the screen would turn black for one frame. On the next frame the screen would also remain black except for patch where the duck is which would be white. If there was more than one duck then this would repeat so each duck got its own single frame with a white patch. The gun had a sensor in it and if it detected white light then it would register a hit and by which frame it detected it on would tell it which duck.
The light gun was designed to look for bright lights in the middle of its field of view. When you pressed the trigger, the screen would turn black for a split second, except for a white square that represented the target. Your light gun would look for that square and send a signal back if it saw it.
You can sort of see it if you look closely. It worked better on CRT TVs.
When you pull the trigger, the entire game screen renders black for a short period. Then the screen displays a white square over the areas that are a “hit” for a short period. Then the game continues displaying as normal.
The gun has a sensor inside that knows how long “a short period” is. So when you pull the trigger, the sensor checks if it sees all black, then it checks to see if it seems to be pointed at a white square. If it doesn’t see BOTH the black and the white square and they aren’t timed perfectly relative to the trigger being pulled, you missed. If it sees them both, you hit.
The reason for that quick black flash has to do with dealing with cheaters. Earlier versions of this tech skipped that part, and people figured out if you pointed the gun at a light bulb, you’d always “hit”. Since the NES gun checks for darkness THEN light, you’d have to somehow pull the trigger and be very good at precisely turning a light on and off.
This doesn’t work as well on LCD TVs because they don’t always change their pixels with the exact timings that CRTs did. Sometimes they do, sometimes they don’t.
The “zapper” (the gun) is just a light detector. When you pull the trigger while playing duck hunt, it does 2 things:
* turns on the light detector
* makes the screen pitch black except for a white square wherever a duck was
If the gun is pointed at the bright square the light detector will notice and register a hit.
If you point the gun at a light source like a brightly lit bulb it will always register hits.
I’m not sure how it resolved *which* target you hit for rounds with multiple targets, though.
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The cool thing about it working this way was that you could play the game using a mirror. My friend had a mirror opposite his TV, we would next to the TV and shoot towards the mirror. Due to the light refraction, when you hit a duck in the mirror, down it went! Good times 😄
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When you pulled the trigger it flashed the screen. The target would flash white, everything else flashed black. That told the gun whether it was facing a target or not. Changing how the targets blink would tell the gun which type of thing it was pointing towards.
Light guns for later consoles were a bit more sophisticated. It would collect data from an entire frame, and see when the light from the tv scan for the frame would cross in front of its sensor. Once it detected that, it would tell the console where in the frame it was detecting, which the console would then used to determine where you were pointing. This allowed it to work without flashing the screen.
This doesn’t work with non-CRT displays, however, and so it’s obsolete, which is why it was replaced with motion-detection.
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