Forgot your password?
typodupeerror

How the Wiimote Works 135

Posted by Zonk
from the little-tiny-marios dept.
The New York Times' 'How it Works' series touches on a remote with a twist: the Nintendo Wiimote. The article describes the micron-sized machines that make it work, displays cut-away graphics of the little white marvel, and rounds out the discussion with a breakdown of where the tech came from. From the article: "The controller's most-talked-about feature is the capacity to track its own relative motion. This enables players to do things like steer a car by twisting the remote in the air or moving a game character by tilting the remote down or up. 'This represents a fabulous example of the consumerization of MEMS,' the tiny devices known as micro-electro-mechanical systems, said Benedetto Vigna, general manager of the MEMS unit at STMicroelectronics, a leading maker of the accelerometers embedded in the controllers. (Nintendo itself declined to talk about the controllers' inner workings.) He said the motion sensors, using the technology that activates vehicle air bags, can accurately sense three axes of acceleration: up and down, left to right, and forward and backward."
This discussion has been archived. No new comments can be posted.

How the Wiimote Works

Comments Filter:
  • Wait... (Score:5, Funny)

    by Anonymous Coward on Thursday December 21, 2006 @11:51AM (#17325368)

    can accurately sense three axes of acceleration: up and down, left to right, and forward and backward.
    Wait, isn't that six axes? Oh, I guess it's just Sony that likes to make shit up.
    • Re: (Score:1, Redundant)

      by cHALiTO (101461)
      No, it's three AXES. What you're talking about are DIRECTIONS.
      • Re: (Score:3, Funny)

        by jizziknight (976750)
        *WHOOSH*

        You might want to have your sarcasm detector checked.
      • Re: (Score:3, Funny)

        by Daemonstar (84116)
        But naming the SIXAXIS the SIXDIRECTIONS just doesn't have the same appeal.
        • Besides motion sensing, both the PS3 and Wii controlers use Bluetooth. I can't help but remember a while back when Slashdot and others were saying Bluetooth is dead [google.com].

          I'm personally hoping this mainstream use and the improvments in version 2, will lead to more mice, keyboards and other devices that use it. It would be nice to have it built right into desktop PCs like it is in some notebooks. Being able to easily use your Wiimote or sixaxis on the PC, or your wireless keyboard and mouse on the consoles, wou
        • by tprime (673835)
          Yeah, it's extra cool that you can spell it FORWARDS and BACKWARDS. Just the name itself is TWOAXIS

          (for those two slow S I X A X I S = S I X A X I S backwards)
    • by EnglishTim (9662)
      The six axes I think refers to being able to sense acceleration in each axis plus rotation around each axis.
    • by Thansal (999464)
      as was pointed out, it is 3 axis, however it tracks movement and twist around each.

      Then again, so does the WiiMote.

      The article does not add anything new to our knowledge of how the nifty little toy works, and it does leave out the fact that the wiimote track rotation as well as movement.
    • by cnelzie (451984)
      It can actually sense (at least) 4-Axis motion, do to the ability of the remote to sense a spin along it's centerline.

          Take a Wiimote, watch the hand pointer on the screen and rotate the Wiimote along it's centerline axis. The pointer hand will rotate on the screen along with the rotation of the Wiimote.
      • by webrunner (108849)
        There's an accelerometer and the pointer.

        The accelerometer returns acceleration along 3 directions, with relation to the remote. This allows it to detect tilt by figuring out which way gravity is, giving it 3 rotational axises.

        The POINTER system can determine a) how far off in what direction the sensor bar is from where the remote is pointing, b) how far away from the sensor bar the remote is and c) The rotation of the remote with respect to the sensor bar.

        THis means the wiimote basically has two ways to d
        • That doesn't sound right.

          The accelerometer returns acceleration along 3 directions, with relation to the remote. This allows it to detect tilt by figuring out which way gravity is, giving it 3 rotational axises.

          How can you infer gravity's direction purely from the local linear accelerations? If your acceleration vector is , okay, you know which way gravity is. But what if your acceleration vector is ? Which component is due to me moving the WIimote and which component is gravity?

          Also:

          The POINTER system c
          • In my last post, I missed that the vectors were hidden because I used the tag containers.

            The first should be [0,0,-9.8] and the second should be [15,15,15].
          • by Mr. Hankey (95668)
            FWIW, Red Steel calibrates your screen size by having you point at objects in the beginning. Integrating acceleration information with previously known absolute information is prone to error from what I've seen, even with significantly more expensive systems, but using just the relative information is a reasonable approximation when you're playing a game.
            • FWIW, Red Steel calibrates your screen size by having you point at objects in the beginning.

              The fish thing? That's not really a calibration. That's just telling you to move *its* assumed pointer location onto *its* objects. That has nothing to do with whether *its* assumed pointer location is where you're really pointing.
          • by grumbel (592662)
            ### How can you infer gravity's direction purely from the local linear accelerations?

            Games that use tilting for anything important don't expect the player to make any motions, so getting gravity in those games is easy since the motion vector is always [0,0,0] and the gravity vector is the only thing you ever see. Combining exact tilt with full motions should however get pretty tricky, might even be pretty much impossible for any real world scenarios.

            ### I suspect there is a separate tilt sensor, similar to
            • Nope, there is just the accelerometer and the sensorbar, no other sensor in the Wiimote. That the sensorbar can detect tilt in one axis is simply the result of having two (or more) IR dots. available, tilt detection in racing games works via the accelerometer, the tilt info from the sensorbar might be used for those funny pointer rotations.

              Actually it (the sensor bar) is most likely used to correct drift. In the VR industry this would be called a six degree of freedom hybrid inertial tracker. The primary me
      • "Take a Wiimote, watch the hand pointer on the screen and rotate the Wiimote along it's centerline axis."

        I will do that as soon as I GET ONE!!! sheesh thanks for reminding me that I can't *sobs*
      • It can actually sense (at least) 4-Axis motion, do to the ability of the remote to sense a spin along it's centerline.

        Ummm...no, that would still be the 3rd axis, running from you to the tv (if you are holding it in a normal remote control orientation), and the movement would be known as roll. The other rotations (and axis) are yaw (around the axis from floor to ceiling) and pitch (along the axis from your left to your right). The other 3 degrees of freedom are the translations along those same 3 axis.
    • by miro f (944325)
      I believe sixaxis involves three axes of movement and 3 axes of rotation, making 6 total.

      Shhh... don't tell anyone these are the same three axes!
    • I assumed that the whole SIXAXIS business came from the fact they have those three axes plus the d-pad and two analog sticks.
  • by xxxJonBoyxxx (565205) on Thursday December 21, 2006 @11:58AM (#17325436)
    How the Wiimote Works


    C'mon, "editors"...this is SlashDot, not Time. Most people here could probably have written that article blindfolded. How about a couple of real tech articles today?
  • by Zero Degrez (1039938) on Thursday December 21, 2006 @11:59AM (#17325452)
    This just in.

    Nintendo is using their wiimote technology to determine when the wiimote flies from the users hand, and will now deploy an airbag before striking your HDTV.

    Please return your wiimote for the new version with the wiirbag.
    • Re: (Score:1, Funny)

      by Anonymous Coward
      You mean "Wiibag", surely. Or "ColostoMii Bag".
  • by abigsmurf (919188) on Thursday December 21, 2006 @12:00PM (#17325462)
    The sixaxis must be twice as good! Either that or Sony failed geometry...
    • Someone should tell Sony that thier controllers are also moving through time. Maybe they'll release a clock upgrade to make it an EightAxis.
  • Analogies rule!!! (Score:5, Interesting)

    by jibster (223164) on Thursday December 21, 2006 @12:01PM (#17325474)

    These accelerometers are so sensitive, Mr. Vigna said, because electrons -- those subatomic particles that whirl around the nucleus of atoms like a video game in the making -- can sense the subtle atomic-level movement of the silicon structures.
    Even for /. that's a messed up analogy. How is an electron like a video game in the making? Or is it the whirling around the nucleus that resembles the video game creation process?
    • Re: (Score:3, Insightful)

      by eln (21727)
      Endlessly spinning in circles, never actually getting anywhere? Sounds like a pretty typical development environment to me.

      • by Thansal (999464)
        Only if you follow games like Dikatana and Duke3D.....

        and zelda, and Valve games....

        and..

        oh alright, you win.
      • ... and the more you try to peg something down, the more uncertain the rest of the thing is.
      • by steveo777 (183629)
        I'm still wondering what the electron is doing whirling around in the nucleus.. How the hell did it get in there?!
    • by ThinkWeak (958195)
      So that's how they do it? I always thought video games were made with magic.
  • by Speare (84249) on Thursday December 21, 2006 @12:01PM (#17325482) Homepage Journal

    I thought the Wiimote worked like this:

    If you see a monster, throw the Wiimote directly at the monster. Depending on your aim, the monster will die in a shower of bright sparks and crackly noises, or the monster will hurl various objects back at you such as books, chunks of plaster, ceiling fan blades, or your little brother's eyeball.

    • If you see a monster, throw the Wiimote directly at the monster. Depending on your aim, the monster will die in a shower of bright sparks and crackly noises, or the monster will hurl various objects back at you such as books, chunks of plaster, ceiling fan blades, or your little brother's eyeball.
      --


      I always use a +2 Wiimote for my games.
  • by Rosco P. Coltrane (209368) on Thursday December 21, 2006 @12:01PM (#17325484)
    independent researchers have shown that there is a strong link between very high voltages coming from the accelerometers and the state of inebriation (and perhaps low IQ) of the player...
  • So did they actually use tools to open the Wiimote up carefully? Or did they fling it with all their strength at an HDTV to get both an article, and piece of the class-action? [slashdot.org]
  • by Anonymous Coward
    After having used my Wii and the controller for a couple weeks now I've been somewhat disappointed with the technology.

    First, the Wiimote isn't an absolute pointing device. It's all relative to the Wiimote bar you place near your TV. Everything is relative to that device, so you are never actually pointing accurately at anything on your screen.

    Second, the Wiimote has accuracy/responsiveness issues. Not sure if it is interference from bright lights or some other type of wireless/electronic devices. There are
    • by Daemonstar (84116) on Thursday December 21, 2006 @12:14PM (#17325602)
      It's all relative to the Wiimote bar you place near your TV. Everything is relative to that device, so you are never actually pointing accurately at anything on your screen.
      That's because the bar provides the infared source so the Wiimote has a frame of reference for the TV screen. Since it provides the infared source, anything that may alter the source will interfere with the Wiimote (i.e.: shiny surfaces like a coffee table, glass, mirrors, etc.). Of course, it is also why you can substitute the bar for 2 candles [wiihaveaproblem.com].
      • That's true, but that's not what he was talking about. (Well, he was, but not in the part you quoted.) He was talking about how the place where you're really pointing is not the same as where it thinks you're pointing, and you can verify this yourself.

        If you stand close to the TV -- not so close that it goes haywire, but close -- you'll see that it thinks it's pointing way off, depending on how you point, and usually in the vertical direction it's the most severe. And unlike the sibling poster said, this
        • Re:Not informative (Score:5, Interesting)

          by Telvin_3d (855514) on Thursday December 21, 2006 @01:41PM (#17326694)
          Why would you want to have to calibrate it for the TV? The way it is set up right now, it is all relative. It doesn't have to aim exactly where you are pointing, it just has to change its position based on your movements in a consistent manner. The way it is now, i can go from a 23 inch TV to a 9 foot wide projector image with absolutely no calibration. Plug it in and go. That's really special.
          • Why would you want to have to calibrate it for the TV?

            Well, that's my point. You *shouldn't* have to. I completely agree with allowing the simple "above or below" quick setup. My complaint was that it doesn't allow you to provide it more information so that it can use a different algorithm, if you desire, that is more accurate for your particular screen. And the "consistency between screens" isn't necessarily good. It means if I have a smaller-than-usual screen (a pitiful 23'', poor me) I have to keep
            • There are extra options you can define in the game. For instance in Zelda you can define the width of the sensor-bar on your TV. I can't speak for RS however since I didn't buy that one. As for games like Time Crisis or House of the Dead that'll make their way onto the Wii eventually (yay, no flashing screen crap). You can be sure they will implement other ways to calibrate for a more "dead on" aim. For the current games? Theres no point! If you had to calibrate each time you sat down, the console would be
              • Theres no point! If you had to calibrate each time you sat down, the console would be a horrid failure.

                Really? You have to tell it whether the sensor bar is above or below, each time you play?

                No, it's stored in the OS. Like the calibration settings would be!

                Most people can't calibrate gun games correctly.

                They can't expand a rectangle to their screen boundaries?
        • The problem with it "becoming chaotic" if you sit too closely is that the Wiimote has to see both IR sources at the same time in order to tell where it is pointing; if you go too far away you would have a similar problem as the Wiimote would see both IR sources as one light source (I'd assume this would probably happen at quite a distance. Nintendo designed the Sensor bar to be optimal in most situations (between 6 and 15 feet from the television I would assume) but if that doesn't work well for you (and yo
          • Did you understand what I was talking about in my previous post? I'm not having "problems". My Wiimote is doing exactly what it's designed to do. The problem has nothing to do with hardware either. The two IR sources suffice to figure out where it's pointing. My complaint was that the Wiimote takes its view of the IR's, and uses a pre-defined formula for placing the crosshairs, when really it should allow you to give it more information about where your screen really is, so it can modify the formula so
        • Shooting games (House of the Dead, etc) would no doubt work they way they always have, by reading the pixel colour on the screen. Any motion sensing madness is really just a bonus - and I guess would all help in the calculation and maybe make it more accurate. Its not like you haven't been able to buy gun based games on older systems, like the Dreamcast.

          Also, it wouldn't surprise me if you larger/more powerful sensor bars were on sale at some point in the future - if not from Nintendo, then from 3rd partie

          • Shooting games (House of the Dead, etc) would no doubt work they way they always have, by reading the pixel colour on the screen. Any motion sensing madness is really just a bonus - and I guess would all help in the calculation and maybe make it more accurate. Its not like you haven't been able to buy gun based games on older systems, like the Dreamcast.

            Well, my point was that, if calibrated, the Wiimote could know where you're really pointing, *without* having to read the pixels on the screen. It would ju
        • Re: (Score:2, Insightful)

          by KDR_11k (778916)
          I assume the firmware is trying to keep it simple so people won't get confused by basic settings. A game that needs correct aim could always add those calibration options (of course it'd be better if the firmware could store that config so you don't have to redo it for every game, maybe once the lightgun games come out Nintendo will consider adding it to the firmware).
          • I assume the firmware is trying to keep it simple so people won't get confused by basic settings.

            So, in other words, you weren't able to read allllll the way to the part where I said:

            "Sure, I can understand them not *forcing* you to calibrate like that on startup, but to not even bury it under some advanced options?"

            Again, to repeat myself unnecessarily, I understand them not making that a basic or a startup option. I don't understand why they wouldn't give you that option *at all* in the OS.

            See sig.
    • by nuggz (69912) on Thursday December 21, 2006 @12:14PM (#17325614) Homepage
      If your wiimote is a little off make sure you check the sensitivity to calibrate it.
      I found that made a huge difference.
    • It has been suggested before, but try re-calibrating your remote. I have 3 friends with Wii's, at least two of them would have bitched non-stop if they had the problem you're having.
    • by El Gigante de Justic (994299) on Thursday December 21, 2006 @01:26PM (#17326476)
      First, the Wiimote isn't an absolute pointing device. It's all relative to the Wiimote bar you place near your TV. Everything is relative to that device, so you are never actually pointing accurately at anything on your screen.

      I don't think it ever was lauded or presented as an absolute pointing device prior to its release, but it is a very good ubiquitous pointing device and not simply a one trick pony as something like the Zapper was. As stated by others before me, this is because the sensor bar emits the IR which the wii-mote triangulates its pointing position from. It definately works best on the top of the TV, IMO. Ideal setup can vary depending upon whether you are typically sitting or standing, how high your TV is relative to the ground/seat, etc. Calibrating it is important too -- in my mind, that's one of the things that killed Red Steel - you can only calibrate at the very begining of the first level and not from the pause menu while pointing is an essential part of the controls. In Zelda:TP, you can play entirely without using the pointer and it still has a more advanced calibration option than the beginning of Red Steel available at all times (if only you could turn down the tingling fairy sound).
            It would not be possible to have an absolute pointer that would work on all TVs; they would have to actually sell a Wii TV (a Wii-V?) with the IR beams behind the screen to make an absolute pointer. The reason the Zapper and other light guns worked as something like an absolute pointer is because the tech was different, and as I understand it will not work on some modern TVs (I can't recall if its LCD or Plasma). When you pulled the trigger on the Zapper, the screen flashed black for a frame, and the area around the target sprites flashed white after that to indicate a target. The photo-receptors in the Zapper would detect that different to determine a hit or miss. Would you really want the screen flashing right with every shot in any modern FPS? The problem with using something like an invisible later pointer is that TV screens are not flat, and are usually convex. To do a reflective pointer you would ideally want a concave screen with the player at the focal point. By using IR and having each Wii-mote figure out its own position, you don't have to worry about different controllers interfering with each other's signals, etc.

      Second, the Wiimote has accuracy/responsiveness issues. Not sure if it is interference from bright lights or some other type of wireless/electronic devices. There are times where you are having to repeat the same motions over again because the Wiimote isn't registering.

      If you're having accuracy/responsiveness issues with the pointer, your most likely culprits are 1) other bright lights (including sunlight) in your gaming area 2) Other heat sources that aren't lights in the gaming area (i.e. laptop with running harddrive on the coffee table) 3) possibly reflective surfaces, but doubtful. If you aim your Wii-mote away from the screen and happen to pass another heat source like a candle or laptop, it may temporarily focus on that for triangulation, causing all sorts of problems, so keep your gaming area free of IR sources that can distract the remote. Lights should only be a problem if they are also a significant heat source (incandescent bulbs), and darkened rooms are better for gaming anyway.
            I haven't had any obvious problems with Wi-Fi, but it and Bluetooth do operate in the same range, as do most cordless phones. If you're having response problems regularly, try changing the set channels on your Wireless router and/or cordless phones.
            As for response issues with other motions, I have occasionally noticed some problems (like with batting in Wii baseball), where the bat seems way off, but if you go back to a base position and restart your motions, it usually comes out just fine. One of the tricky parts to motion recognition is determining which motions were deliberate and which are casual motions not meant to take an action. I much more often accidentally do something with a casual motion than have actions go undetected.

      • It would not be possible to have an absolute pointer that would work on all TVs

        Actually, it would be possible. You would need to have IR sensors at opposite corners of the TV. The Wiimote already knows it's own roll, so the biggest problem would be dealing with your angle to the side or above/below the TV. Having 4 IRs (one for each corner) might make that a lot easier.

        Interestingly, I seem to recall that this is how the Wii worked when it was first announced (2 sensors in opposite corners). I was actually
    • I thought the same thing as you when I first got my Wii. It seems like you're just moving the Wiimote to get a sympathetic motion of the cursor, but that the Wiimote isn't actually pointing at the cursor. For me, it feels like I'm pointing a bit below the on-screen cursor.

      But try this: hold the Wiimote up to your eye, and look along the Wiimote like using the sight on a handgun. In actual fact, it lines up perfectly, at least for me. It just doesn't feel like it does. I'm not sure why.

      • by Aladrin (926209)
        I've done that. Mine is not even close to accurate. The best I can get is if I put the bar right under the edge of the display. At that point, 2 inches top and bottom are not considered screen and pointing at those areas is 'off screen' to the wiimote.

        The Wiimote does not calibrate for the size of the TV, so it -cannot- be accurate on all TVs. Apparently somewhere around 33" is about right.

        I suspect this would not be nearly so annoying if my TV was smaller than that, as you tend to overshoot when you ar
    • It's all relative to the Wiimote bar you place near your TV

      Well, duh. The Remote can't know where you place your TV, or how big your TV is. That's why there is a sensor bar. Games are free to calibrate your remote, though, so that the "TV offset" is corrected. So far, none do this. You could fix this by creating your own wider or smaller sensor bar - I thought about creating a small white sensor bar I can place inside my projector's picture.

      The responsiveness issues seem to depend on the games. Some hav

  • ..to the Wiimote [sparkfun.com] - at least reversed from the eeprom on the device. This should improve the compatibility of PC's to the Wiimote, and I hope we see some interesting applications on the PC soon ; that or Nintendo should release a Wii-SDK, otherwise I think they are definitely losing a whole lot of interest in the long run of the more adventurous type of user who longs for interesting applications for this simple (proven) but now widely available concept of three-axis sensing devices.
  • Motion or angle? (Score:3, Insightful)

    by seebs (15766) on Thursday December 21, 2006 @12:53PM (#17326084) Homepage
    I'm a bit confused. The ability of the Wiimote to sense the angle it's at seems quite consistent, and doesn't appear to be possible to "fool", while the ability to sense motion can be fooled somewhat.

    It seems to me that they must be separate, at least a little. You can walk away with a Wiimote, far out of bluetooth range, turn it however you like, bring it back... And the console will still sense its orientation precisely. Location? Games that use that sometimes get out of sync so you have to wave the Wiimote around a bit to get them better calibrated.

    So I'm pretty sure that's a separate feature, to say nothing of the additional component of the CCD pointing at the IR sources above your TV to give you a pointing device.
    • Depends on what you mean by orientation. If you mean the rotation of those pointers like in the Main Miinu (haha, get it?), that's calculated using the Sensor Bar, erroneously named as it is.
    • Re: (Score:3, Informative)

      I'm a bit confused. The ability of the Wiimote to sense the angle it's at seems quite consistent, and doesn't appear to be possible to "fool", while the ability to sense motion can be fooled somewhat.

      There is a reason for that ...

      The Force of Gravity will always register as an (aproximately) 9.81 M/(s^2) acceleration to the acclerometers inside of the Wiimote; this means that you should be able to tell it's orientation in comparison to the ground pretty easily.

      I'm a bit confused. The ability of the Wiimote
      • The Force of Gravity will always register as an (aproximately) 9.81 M/(s^2) acceleration to the acclerometers inside of the Wiimote; this means that you should be able to tell it's orientation in comparison to the ground pretty easily.

        Unless, of course, I'm accelerating it such that the vector appears equal in all directions or something.
        • by Guppy06 (410832)
          "Unless, of course, I'm accelerating it such that the vector appears equal in all directions or something."

          I believe in the business they refer to that as "freefall," and that's what the wrist^Wwarnings to hold on tight are supposed to be there for.
        • You can't have accelerate something in all directions at the same time, an object can only be accelerating along a particular 3 dimensional vector at any given time ...

          If you mean how can it tell where gravity is while you're accelerating it along a different vector, the answer is that it probably can't but that isn't really a problem; essentially, you only have to attempt to re-calibrate for gravity every few seconds (say every 5 seconds) by waiting for a steady acceleration of (approximately) 9.81 M/(s^2)
    • Re:Motion or angle? (Score:4, Interesting)

      by acidblood (247709) <decioNO@SPAMdecpp.net> on Thursday December 21, 2006 @02:05PM (#17326970) Homepage
      Having done some inertial engineering work, I can shed some light on this issue.

      The Wii-mote has accelerometers on it. These sense forces applied to it (gravity included), and their combined output is a vector indicating the direction and modulo of the resultant acceleration. Assuming you're standing still, you'd only be subject to the force of gravity, and by definition it always points to the ground. So do a few vector computations and you know the orientation of the Wii-mote. There is a problem with a `blind axis' (rotation in the same axis as gravity can't be detected), but ignore that for now.

      On the other hand, if you want to estimate position, here's what you have to do: given an initial position, read the accelerometers, subtract the effect of gravity from the acceleration vector (harder than it seems, since the Wii-mote could be pointing anywhere, really), which then gives the `real acceleration' of the system. Now integrate this once to obtain velocity, and again to obtain position. There's just so much room for error here, that I don't know where to start. Limited accelerometer resolution, poor A/D converters, temperature drift, numerical accuracy issues, you name it. Integrating measurements (not only that, but integrating twice!) is just a recipe for disaster. Then there's a fundamental limitation to accelerometer devices: rotations can't really be distinguished from translations. Just think about it -- a given resultant acceleration vector could be the result of pointing the Wii-mote in any given orientation, added to a specific acceleration in a specific direction. You just don't have enough information to distinguish between the two -- not with accelerometers alone, at least.

      Hope that helps.
      • I don't understand. In the second paragraph, it sounds like you're saying the accelerometers can tell which way gravity is, but in the second, you're saying it can't distinguish it from the acceleration due to the motion of the Wiimote.
      • by tprime (673835)
        Wow.. Does anyone remember the classroom scene in Better Off Dead where Lane draws the picture of a pregnant woman when he is supposed to be figuring out a complex math problem? Just before that the teacher jokingly rattles off an explanation to a difficult mathematical quandry and it sounds soooo easy that if you didn't get it you were stupid. After reading that last post, I felt like a moron for not having a freaking clue.

        I am glad there are smart people out there, because I know that if it were up t
      • Then there's a fundamental limitation to accelerometer devices: rotations can't really be distinguished from translations. Just think about it -- a given resultant acceleration vector could be the result of pointing the Wii-mote in any given orientation, added to a specific acceleration in a specific direction. You just don't have enough information to distinguish between the two -- not with accelerometers alone, at least.

        I thank you for your knowledgeable post. Out of curiosity, if they were using more tha

        • by acidblood (247709)

          Out of curiosity, if they were using more than one 3-axis accelerometer like this one would they still have difficulty with determining pure rotation from other movements?

          I believe you mean having a second accelerometer aligned to a different axis. Unfortunately, that doesn't add any extra information; you're still measuring the same physical quantity. Think of this as reading a vector in a canonical coordinate system (say x = (1,0,0), y = (0,1,0), z = (0,0,1)), and then reading the same vector but in a rot

          • I'm not familiar with what mathematics would be involved, but I would think with 2 or 3 of those (each able to read out data for all 3 axis' simultaneously) in strategic spots oriented on different axis', you could reliably work out any motions that happened. But hey, they got it to work very well and that's the important part.

            Perhaps we'll get a better idea if and when someone gives us a real run down of how that wii-mote is laid out.
      • by seebs (15766)
        Very helpful, thanks!

        I think I'd spaced off the availability of a constant acceleration. I suppose that leads to a secondary question: Is it in fact the case that the Wiimote only senses things correctly in a normal gravitational field?

        That does explain why games that try to use "move the Wiimote forwards, backwards, and side to side" as an X/Y plane tend to be hard to play, while games that use the pointer for the plane, and just sense small individual motions, do fine.
        • by acidblood (247709)

          Is it in fact the case that the Wiimote only senses things correctly in a normal gravitational field?

          For orientation (knowing where the Wii-mote is pointing), you pretty much need a gravitational field, since that's a fixed reference: it always points down. In a microgravity environment (or freefall), the Wii just wouldn't know where it was pointing since there's no reference to compare to. Of course, if you need attitude control in a microgravity environment, say a satellite or space station, then you can

  • by J-1000 (869558)
    While I love the Wiimote and Nunchuk, I think they really suffer from the lack of at least a single-axis gyroscope. The accelerometer is great for measuring tilts in relation to the earth's surface, but they can't register angles on axes perpendicular to the earth's surface. This makes it more difficult to register a camera pan to the left or right, for instance, without involving the IR sensor.

    The most obvious use (to me) for such a feature would be to have the Nunchuk pan the camera left and right as you
  • What? (Score:1, Troll)

    by drinkypoo (153816)

    He said the motion sensors, using the technology that activates vehicle air bags

    This is fucking hilarious. I will proceed to let you know precisely how most vehicle air bags are activated.

    It is true that in the more modern vehicles there is ONE accelerometer per direction of air bag. This is used to set off air bags other than the front. There is usually one accelerometer to set off the front air bag.

    HOWEVER this is not the only input. In fact it takes two inputs to set off the air bag. One input

    • Clearly those with modpoints do not know how airbags are set off. I fucked the curve all up in my Automotive Electronics class, and surely know more about it than the idiots who modded me.
      • by cheekyboy (598084)
        Is there a weight sensor on the seat, because say the car rolls off by itself and hits a wall with no one inside it, will the air bags
        still go off and waste them? or are they smart to know no one is in the car? Hmmmmm!!! or is that a BMW only feature.

        Any comments about the decapitated victims of air bags that went off at jogging speed?
        • by drinkypoo (153816)
          Most cars do not know if there is someone sitting in the seat for any purpose, airbags or not. Most cars do not use the seat as an airbag sensor input. As for the "decapitated" victims - never heard of anyone losing their head, although AFAIK there's been a broken neck or two, and lots of broken noses - maybe they should learn how to sit in the car? If your seat is adjusted properly and your hands are in the proper positions on the wheel it's pretty hard to get seriously hurt by an airbag.

"Let every man teach his son, teach his daughter, that labor is honorable." -- Robert G. Ingersoll

Working...