[Flii] New version of FWiidom in svn

Tue Apr 3 06:42:12 EDT 2007

so the wiimote calculates them automatically? Does it do this when the
wiimote is switched on, or at regular intervals? Or am i missunderstanding
and are you calculating them in the c# app, and then storing them in the
wiimote?

On 4/3/07, Pete Hobson <pete at freesome.com> wrote:
>
> Hi Rob,
>
> Yes, we have three values to work with per accelerometer.
>
> 1) the current acceleration (a1)
> 2) the Zero point calibrated value (a2)
> 3) the 1g calibrated value (a3)
>
> a2, and a3 will be available as constants per wiimote (they are stored in
> the wiimote memory) .
>
> On 2 Apr 2007, at 23:49, Rob Bateman wrote:
>
> yes, i was in a bit late today :)
>
> reading the wikipedia article it becomes clearer how acceleration can be
> estimated from the three accelerometer (i'll stop calling them gyroscopes
> now) outputs. One interesting point i noticed was that as the outputs from
> the accelerometers increase (in the positive or negative direction) their
> accuracy decreases. So while it may appear that the z-axis is redundant,
> when either the x or y axes are at an angle close to 90 degrees from the
> vertical, it would be more accurate to include the z axis data in
> calculations as it would be closer to 0 degrees from the vertical.
>
> I also didn't realise the accelerometers could output a normalised reading
> above 1g, so with this in mind it should be possible to calculate
> acceleration independent of gravity effects, if we assume that the
> acceleration occurs in a 'jerk' and the rotation can be re-calibrated at the
> end (which shouldn't be too delayed considering the finite space people have
> to accelerate things given the length of their arms).
>
> i don't have any more time to look at this now (i think i probably need a
> good nights sleep...) but i'll definitely give it some thought over the next
> few days and let you know what i come up with...
>
> also, the whitepaper on gesture recognition is completely useless for
> anyone willing to understand the mechanism, but i'm sure there's more useful
> papers out there.
>
> Rob
>
>
>
> On 4/2/07, Adam Robertson <oldskool73 at gmail.com> wrote:
> >
> > err, yeah, all three are in there, I may not be passing them all through
> > to flash though as i assumed it wasn't all needed :)
> >
> > A
> >
> >
> > On 4/2/07, Pete Hobson <pete at freesome.com> wrote:
> > >
> > >  hey adam,
> > >
> > > can i just confirm you have access to *both* the live acceleration
> > > data , and the 1G *and* zero point calibration data.  All three are needed
> > > to calculate rotation correctly  believe.
> > >
> > > On 2 Apr 2007, at 10:20, Adam Robertson wrote:
> > >
> > > wow, bet someones a bit tired today ;)
> > >
> > > so, I take it it worked for you, that's a good first step!
> > >
> > > this page my be helpful (or may be what you already know)...
> > >
> > > http://www.wiili.org/index.php/Motion_analysis
> > >
> > > ...in fact that page seems to have been updated since I last looked
> > > and have the pitch/roll equations, which I think are the same as we are
> > > using?
> > >
> > > A
> > >
> > >
> > > On 4/2/07, Rob Bateman <rob.bateman at gmail.com> wrote:
> > > >
> > > > Hey guys
> > > >
> > > > i've had a look at the .as files and the output you get from the
> > > > conduit, and looked at how it reacts to the motion of the wiimote
> > > >
> > > > very interesting stuff, and after much waving about, i've made some
> > > > observations which i hope will help with the development
> > > >
> > > > i've not had a chance to compile my own tests, (no as3 on my pc at
> > > > the mo) but from what i've seen of your own, there seems to be some
> > > > confusion over the three gyroscopic outputs (measured as gX, gY and gZ i
> > > > believe, as output in your graph demo)
> > > >
> > > > each one appears to be outputting the sin of the angle of the
> > > > normalised vector from the horizontal. (a normalised vector to a plane
> > > > represents a vector of length 1 extending perpendicularly out of the plane)
> > > > to elaborate:
> > > >
> > > > gX is outputting the sin of the angle of the normalised vector  of
> > > > the right side of the wiimote from the horizontal
> > > > gY is outputting the sin of the angle of the normalised vector  of
> > > > the front of the wiimote (where the ir sensor is) from the horizontal
> > > > gZ is outputting the sin of the angle of the normalised vector  of
> > > > the bottom of the wiimote from the horizontal
> > > >
> > > > in each case, a positive angle is represented as being above the
> > > > horizontal plane, and a negative angle below. So for example, when gY is +1,
> > > > the angle is +90 degrees and the right side of the wiimote is pointing
> > > > straight up.
> > > >
> > > > for the fields in your wiimotecontroller class, pitch can be
> > > > calculated in radians from the arcsin of the gY value, and roll can be
> > > > calulated in radians from the arcsin of the gX value. The gZ value is
> > > > slightly redundant as it doesn't add any information to that already given
> > > > by gX and gY, but i suppose it could be used to smooth out erroneous
> > > > readings from gX and gY.
> > > >
> > > > From examining the fields in the wiimotecontroller class, i'm a
> > > > little confused by the presence of relative acceleration values. I'm unsure
> > > > how these could be calculated to sufficient accuracy with the information
> > > > available, because of the redundance with orientation thanks to Newtons
> > > > second law. The force (acceleration) being applied to the wiimote could not
> > > > be distinguished by the gyroscopes from the force being applied by the
> > > > earths gravity, hence the two vectors would simple multiply together and
> > > > would appear as if the wiimote had been tilted. It may be possible to
> > > > produce something that could be subtracted from the orientation readings
> > > > given by the ir sensor, but only if the wiimote was pointing at the sensor
> > > > bar at the time.
> > > >
> > > > I plan to get my pc set up so that in future i can run tests myself,
> > > > to get a better picture of what is it possible to determine from the output
> > > > available. In the meantime, i hope the above information is useful! :)
> > > >
> > > > cheers
> > > >
> > > > Rob
> > > >
> > > >
> > > > On 4/1/07, Pete Hobson < pete at freesome.com> wrote:
> > > > >
> > > > > Nice one adam.
> > > > > I'll have a look at this under parallels on the mac, will be
> > > > > interesting to see if it works there.
> > > > >
> > > > > One quick question - does using c# bring in dependancies on the
> > > > > .NET framework also, or can you use c# for non .net console apps also??
> > > > >
> > > > >
> > > > > On 1 Apr 2007, at 21:41, Adam Robertson wrote:
> > > > >
> > > > > Hi,
> > > > >
> > > > > I've put my work so far on the new FWiidom c# wrapper in my svn @.
> > > > >
> > > > >
> > > > > http://www.fwiidom.org/svn/
> > > > >
> > > > > there's a quick readme and the start of some bare bones
> > > > > documentation in there too, if you are intrested in beta testing it feel
> > > > > free to have a play and let me know how you get on.
> > > > >
> > > > > Adam
> > > > >
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> > > > >
> > > > >
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> > > > >
> > > >
> > > >
> > > > --
> > > > Rob Bateman
> > > > Senior Creative Developer
> > > >
> > > > Work: 0207 7804841
> > > > Mobile: 07714 329 073
> > > >
> > > > rob.bateman at akqa.com     |     http://www.akqa.com
> > > >
> > > > AKQA, 1 St John's Lane, London EC1M 4BL, UK.
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> > > >
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>
>
> --
> Rob Bateman
> Senior Creative Developer
>
> Work: 0207 7804841
> Mobile: 07714 329 073
>
> rob.bateman at akqa.com     |    http://www.akqa.com
>
> AKQA, 1 St John's Lane, London EC1M 4BL, UK.
> _______________________________________________
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>
>
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>

-- 
Rob Bateman
Senior Creative Developer

Work: 0207 7804841
Mobile: 07714 329 073

rob.bateman at akqa.com     |    http://www.akqa.com

AKQA, 1 St John's Lane, London EC1M 4BL, UK.
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