How do it know?

hotdude729 · 05-19-2002, 09:26 PM

Ok i have a question to ask and if anyone knows then tell me. You know the game "duck hunt" on nintendo where you shot a gun at a screen and it fires where you point. HOW DOES IT DO THAT??!!!! I have wondered since i was like 5 so someone tell me!

MaggieL · 05-19-2002, 10:33 PM

When you squeeze the trigger, the game electronics very rapidly move a small bright square in a scanning pattern across the screen, keeping the background dark. . The gun you're holding contains a single photocell with a small lens system in front of it that causes only the small spot on the screen the gun is pointing directly at to be focused on the photocell.

When the game sees a voltage peak from the photocell, it knows that the currently illuminated square in the screen is the one the gun is pointed at and registers a shot at that screen position. This all happens so fast that all you see is a single big flash on the screen, which looks reasonable as a muzzle flash from the gun.

russotto · 05-21-2002, 02:48 PM

You can only change a given spot on a screen 60 times per second, so it can't scan THAT fast.

MaggieL · 05-21-2002, 04:40 PM

Hmm. Good point. It must not use a single point, even though that's how the old light pen interfaces used to work. Turns out the close integration of console games with their video timing chain holds the clue.

My initial response was that perhaps it was a series of frames with distinct patterns encoding a binary screen address. That would only take as many frames as there are bits in the address...so if the pointing resolution was, say, 300x200 (fairly high, really, it's prolly much lower than that) the highest address would be 0xEA60, no more than 16 bits...you can show 16 frames in around 2600 msec.

OK, that was a good try on my part. But it turns out I was overthinking: here's two real answers (with two real patent numbers to go with them)...I like the second one best. :

http://www.howstuffworks.com/question273.htm

hotdude729 · 05-21-2002, 07:31 PM

Thank you very much for you duck hunt insight. Nintendo can be very thought provoking, it also makes a person feel very stupid. Well anyway i geel smarter and impressed my friends.

05-19-2002, 09:26 PM	#1
hotdude729 Purple Monkey Dishwasher Join Date: May 2002 Location: Dallas, TX Posts: 31	How do it know? Ok i have a question to ask and if anyone knows then tell me. You know the game "duck hunt" on nintendo where you shot a gun at a screen and it fires where you point. HOW DOES IT DO THAT??!!!! I have wondered since i was like 5 so someone tell me!

05-19-2002, 10:33 PM	#2
MaggieL in the Hour of Scampering Join Date: Jan 2001 Location: Jeffersonville PA (15 mi NW of Philadelphia) Posts: 4,060	When you squeeze the trigger, the game electronics very rapidly move a small bright square in a scanning pattern across the screen, keeping the background dark. . The gun you're holding contains a single photocell with a small lens system in front of it that causes only the small spot on the screen the gun is pointing directly at to be focused on the photocell. When the game sees a voltage peak from the photocell, it knows that the currently illuminated square in the screen is the one the gun is pointed at and registers a shot at that screen position. This all happens so fast that all you see is a single big flash on the screen, which looks reasonable as a muzzle flash from the gun. __________________ "Neither can his Mind be thought to be in Tune,whose words do jarre; nor his reason In frame, whose sentence is preposterous..."

05-21-2002, 04:40 PM	#4
MaggieL in the Hour of Scampering Join Date: Jan 2001 Location: Jeffersonville PA (15 mi NW of Philadelphia) Posts: 4,060	Hmm. Good point. It must not use a single point, even though that's how the old light pen interfaces used to work. Turns out the close integration of console games with their video timing chain holds the clue. My initial response was that perhaps it was a series of frames with distinct patterns encoding a binary screen address. That would only take as many frames as there are bits in the address...so if the pointing resolution was, say, 300x200 (fairly high, really, it's prolly much lower than that) the highest address would be 0xEA60, no more than 16 bits...you can show 16 frames in around 2600 msec. OK, that was a good try on my part. But it turns out I was overthinking: here's two real answers (with two real patent numbers to go with them)...I like the second one best. : http://www.howstuffworks.com/question273.htm __________________ "Neither can his Mind be thought to be in Tune,whose words do jarre; nor his reason In frame, whose sentence is preposterous..."

05-21-2002, 07:31 PM	#5
hotdude729 Purple Monkey Dishwasher Join Date: May 2002 Location: Dallas, TX Posts: 31	Thank You Thank you very much for you duck hunt insight. Nintendo can be very thought provoking, it also makes a person feel very stupid. Well anyway i geel smarter and impressed my friends.

05-21-2002, 02:48 PM	#3
russotto Professor Join Date: Jan 2001 Posts: 1,788	You can only change a given spot on a screen 60 times per second, so it can't scan THAT fast.

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