[chuck-users] Bluetooth and Wiimote: a long-term feature request

Inventor-66 at comcast.net Inventor-66 at comcast.net
Thu Apr 17 16:52:09 EDT 2008

Thanks for the responses.  I appreciate your thoughts, but have a different plan in mind.  I am not going to do the tracking with the IR camera of the Wiimote, but rather with the 3-axis accelerometer inside the Wiimote.  Normally one would use two 3-axis accelerometers and some signal processing to get a full 6-DOF (Degree Of Freedom) tracker, but there is a simple trick that uses only one.  What you do is you obtain pitch, roll, and yaw from the gravity vector, or low-pass-filtered component, and the X, Y, and Z from the dynamic acceleration, or high-pass-filtered component.  It isn't perfect but it does save you a sensor.  

Although it is possible to use OSC to get at a Bluetooth HID sensor, that sounds a bit over my head and would require a lot of effort and knowledge.  It would be simpler to build a custom USB accelerometer using the Ultimark A-PAC Version 2 USB interface and one or two ADXL330Z accelerometers, on breakout boards from SparkFun Electronics.  

On the bright side, while exchanging posts with Kassen on the forum, we both separately noticed that there is a trend in the gaming industry, and we are expecting many new 3D mice and joysticks that are based on the now-inexpensive 3-axis accelerometer chips that are available from a few manufacturers.  Kassen identified one for only $20 that hooks up to USB, looks like a joystick, and detects pitch, roll, and yaw.  That's today, and in a few months there should be many to choose from.  So my game plan is to wait a little while.  Cash-wise, I am broke any way due to a massive car repair, so this will be a nice exercise in patience and careful planning, lol.  

What am I planning to do with a guitar tracker?  Why, lots of stuff!  I'm sure you can imagine the many things that could be done, and here are some of them.  1.  Add increasing amounts of negative feedback as the guitar is pointed down to the ground, and positive feedback as it is pointed up to the sky.  2.  Add reverb as the guitar is rotated toward the audience and echo as it is rotated back away from the audience.  3.  Vary the feedback delay duration according to the player's leaning forward or back.  That does something with all three orientation axes of pitch, roll, and yaw.  Now that we've got the performer gyrating around on stage like Angus Young of AC/DC to access all of the tonal possibilities, let's deal with walking around on stage.  

If the player walks back to center, rear of the stage where the drummer would normally be in a typical rock band setup, the computer recognizes this and substitutes drums for the guitar notes that are being played.  This is done with an FFT and a peak tracker, set up so that new fundamental frequencies trigger synthesized drum beats as they arise.  The player may then record a drum loop by smacking the guitar, playing the loop, and smacking the guitar again.  Now that drums are playing, the player walks to stage front, right where the bass guitar would normally be and ChucK's pitch shifter kicks in, making the six-string sound like a bass.  Executing the same looping trick, the player initiates a repeating bass guitar riff.  Now moving to stage front, left or stage front, center the player can then play the lead guitar part of the song as well as sing.  To add to the tricks, singing in stage front, left creates a talk-box or vocoder type effect for those "Mr. Roboto" moments!
  that w
e all enjoy.  

Finally, when the player jerks back on the guitar creating a gun-recoil motion as if something just shot out of the headstock of the guitar, that tells the computer to switch between modes.  Planned modes are "normal", "thunderstorm", and "war".  In these modes, the guitar plays through but each new note initiates a ChucK-based sound effect such as thunder or rain, else bombs, machine guns, and explosives.  I'd like to pretend I'm Angus Young playing "Thunderstuck" with real thunderstorm sounds under guitar control.  The angular and positional features previously described are available in all modes.  

Also, I should probably mention that my secret motivation for doing this is to create some kind of exercise machine that I will actually use.  If I need to bend over or walk around to achieve various guitar effects, I'll probably actually do it and get a mild workout.  Then I will become a leaner, meaner, guitar-playing ChucKist, or so I hope.  Do you have any other wild ideas for what to do with an instrument tracker?  As always, I welcome your comments and suggestions.  

"Forget all about that macho stuff and learn how to ChucK guitar!"


p.s. I sent an email to Fender, the famous guitar manufacturer, suggesting the above.  Who knows, maybe they'll make a guitar tracker product for us to enjoy.  

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