How the Wiimote Works 135
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."
Wait... (Score:5, Funny)
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You might want to have your sarcasm detector checked.
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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
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(for those two slow S I X A X I S = S I X A X I S backwards)
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Re:Wait... (Score:5, Funny)
That's why they should have called it something super-awesome like Axis of Threevil.
But you could (Score:1, Offtopic)
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That said, there are still only three of them in the case of the PS3 controller, even if it can sense rotation about and motion along those three axes. But nobody would have bought the 6DoF.
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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.
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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.
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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
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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
CORRECTION (Score:2)
The first should be [0,0,-9.8] and the second should be [15,15,15].
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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.
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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
It uses both for rotation. (Score:2)
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
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I will do that as soon as I GET ONE!!! sheesh thanks for reminding me that I can't *sobs*
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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.
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Shhh... don't tell anyone these are the same three axes!
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Little low-tech for SlashDot, eh? (Score:3, Insightful)
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?
Not troll (Score:3, Insightful)
Time is very dumbed down, and uses slang my middle school English teacher wouldn't allow. That's for non-technical articles.
The NY Times article doesn't tell us anything we didn't already know.
Re:Not troll (Score:4, Funny)
That's not very nice. I mean they named you as "Person of the Year" after all, didn't they?
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Unfortunately I've got enough vampire in me that I don't cast a reflection in cheap psuedo-mirrors like the one on the cover.
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Have a good luck arounnd WiiLi [wiili.org] for more Wii goodness.
Air bags? Perfect! (Score:5, Funny)
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.
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only three axis? (Score:4, Funny)
Eightaxis (Score:1)
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But the latter might be more appealing to people whom like to watch FOX News etc. "The Wii gives you motion tracking, but does it give you FREEDOM?"
Then again, Americans might object to getting their freedom from Japan...
Analogies rule!!! (Score:5, Interesting)
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and zelda, and Valve games....
and..
oh alright, you win.
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simplified "how it works" (Score:5, Funny)
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.
Re:simplified "how it works" or why U dodge (Score:1)
--
I always use a +2 Wiimote for my games.
Imagine the possibilities (Score:3, Funny)
No disassemble!! (Score:2, Funny)
Didn't Live Up To The Hype (Score:2, Informative)
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
Re:Didn't Live Up To The Hype (Score:5, Informative)
Not informative (Score:2)
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)
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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
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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?
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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
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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
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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.
Re:Didn't Live Up To The Hype (Score:5, Informative)
I found that made a huge difference.
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Re:Didn't Live Up To The Hype (Score:5, Informative)
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.
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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
Pointing IS accurate (Score:2)
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.
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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
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Some points (Score:2)
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
And the firmware is available too.. (Score:2)
Motion or angle? (Score:3, Insightful)
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.
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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
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Unless, of course, I'm accelerating it such that the vector appears equal in all directions or something.
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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.
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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)
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Sure, if you throw your Wiimote off a cliff and put some spin on it in the process, you'll confuse the Wii. But I don't think Nintendo cares if the readings are wrong then. They probably did engineer it to survive the fall though (see the GameBoy a
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Re:Motion or angle? (Score:4, Interesting)
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.
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I am glad there are smart people out there, because I know that if it were up t
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I thank you for your knowledgeable post. Out of curiosity, if they were using more tha
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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
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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.
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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.
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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
The one missing feature (Score:2, Informative)
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)
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
abuse of moderation (Score:2)
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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?
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