- chuck-users - lists.cs.princeton.edu

Calculating Motion with Accelerometers
by Inventor-66＠comcast.net 22 Apr '08

22 Apr '08

Regarding methods for caclating motion with accelerometers: For the two sensor approach, you subtract the two linear accelerations to get an angular acceleration, and I believe you also divide by the distance between them. Then you integrate to get angular velocity and integrate again to get angular position (orientation). To get the X, Y, Z position you just pick one of the sensors and integrate to get velocity then integrate again to get distance. Now that I think about it, you'd have to remove the gravity vector by taking the high-pass filter of the acceleration with a low cutoff frequency first, or else by subtracting it off. The "trick", as i understand it, is to take advantage of the gravity vector so you only need one sensor. In this case you low-pass-filter the acceleration to get it's "DC" or "near-DC" component, which should give the orientation vector. Then you high-pass-filter the acceleration to get it's X, Y, Z component and integrate twice to get distance. It's a touchy sort of trick that requires tweaking and yes, it probably doesn't do so well with sudden motions. I'm not sure how well either would work, but I'm going to experiment and give it a try. Les (Inventor)

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Re: [chuck-users] Bluetooth and Wiimote: a long-term feature request
by Inventor-66＠comcast.net 21 Apr '08

21 Apr '08

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!" Les (Inventor) 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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1.2.1.1 ASIO? Please?
by Kassen 21 Apr '08

21 Apr '08

Fellow ChucKists, Does anybody have a win-ASIO version of 1.2.1.1 or the time and means to roll me one? Please? I know it's only a minor upgrade over 1.2.1.0 but I really need the updated Envelope on Windows with good latency. Electro-music.com would have space for hosting or a attachment to me would be fine as well. Let's not send files that size to the list. Yours, Kas.

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Simple percussive sound synthesis
by Jeff Smith 20 Apr '08

20 Apr '08

I'm interested in exploring sound synthesis using ChucK.In particular I'm interested in algorithmic synthesis of simple physically-based sounds, like a water drip or a hand-clap. Does anybody have any examples lying around that create a sound like this from scratch? I'm a complete noob when it comes to audio signal synthesis, and I'd love to see how others have approached building up the sound. -- Jeff Smith Computer Science Dept. University of Saskatchewan

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Guitar HID
by Inventor-66＠comcast.net 20 Apr '08

20 Apr '08

> 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. Actually, I tried sending Midi from Osculator (osculator.net) once (using my wiimote to control the pitch of a Nord Modular), and that wasn't very hard at all. For me at least, it is several orders of magnitude easier than the hardware stuff you suggest :) And since the site says Osculator supports OSC forwarding (gotta try that out later), and receiving OSC messages in ChucK is a breeze, that should be worth checking out. That is, if you use a Mac :/ /Stefan HaHa, I guess we're different animals, Stefan, as a hardware approach seems easier to me. I did get some excellent help from some folks on the forum and tried to compile a program to do this, but it wouldn't compile. Apparently I need dependency files, sigh. Then I started realizing what I really should have realized first, which is that the code is for Linux only and I'm on a Mac, plus none of my machines even have a Bluetooth interface! So the Wiimote is not a solution for me just yet. It looks like USB is going to be best for my situation. Also one nice thing about the whole project is that it's by no means a one-shot deal. I'll likely end up with several HID products before I'm done. I started getting a little stressed out about choosing the right sensor, but when I realized that it will be a journey and a process rather than a decision, I felt a lot more relaxed about it. So I'm jumping on the HID bandwagon, albeit ever so slowly. Les (Inventor)

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Re: [chuck-users] A problem with the code
by pibsid＠suomi24.fi 19 Apr '08

19 Apr '08

A quick glance over your code suggest that the seq faults are caused by float functions that do not return anything. Try: fun float foo(){ return 0.0; //remember to return a float } The null pointer exceptions are propably caused by using SinOsc @ s[MAX_COMP]; This creates an array of null pointer SinOscs. Try without the @: SinOsc s[MAX_COMP]; -Pyry Pakkanen

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Bluetooth and Wiimote: a long-term feature request
by Inventor-66＠comcast.net 17 Apr '08

17 Apr '08

I've been researching 3-axis accelerometers and have decided to build my own joystick HID unit. This will require custom homemade circuit board construction, though not much of it, and the purchase of two $35 circuit boards from the web. So no problem, it should work great and then I can code ChucK to know the position and orientation of my guitar at any moment in time. ChucK can then do many interesting special effects to the guitar sound with that information, freeing the player from clumsy pedals and such. It should be kewl, but along the way I learned that there are many Bluetooth HID products which would have done the job without any special circuitry at all. In fact, a $50 Wiimote - the remote control for the Wii console game - is a perfect little instrument tracker plus it has buttons and such as well, but ChucK doesn't know how to talk to a Bluetooth sensor. So you can see that there is good reason to add Bluetooth HID to the list of ChucK's features. I wouldn't place it at high priority since the dev team is currently so pressured with feature requests and this is only one application. Still, I wonder if such a feature as Wiimote instrument tracking might help to popularize ChucK? Whatever, just making a feature request. I added it to the bottom of the Wiki feature request list. Keep on ChucKin'! Les Hall (Inventor)

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OSX updates =< real-time audio?
by Ge Wang 16 Apr '08

16 Apr '08

Greetings, We are experiencing some rather unfriendly real-time behavior on OS X, seemingly after doing the latest apple upgrades... here are some details, at least on my machine: * system: Macbook Pro / OS X (10.4.11) * updates: Quicktime 7.4.5 + MPB EFI Firmware Update 1.5 * symptoms: real-time audio "goes to poop", even under moderate loads. * workaround: running command line chuck in BLOCKING mode (via --blocking) seems to work, however the default CALLBACK mode seems completely hosed, even with bigger buffer sizes. This is especially problematic for the miniAudicle, which doesn't have the option currently to choose between blocking vs. callback. Has anyone else noticed similar behavior, either on Tiger or Leopard? Or is this an isolated case for my system? We'd appreciate any input! Thanks!! Best, Ge!

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low overhead interpolation trick
by Kassen 12 Apr '08

12 Apr '08

Dear ChucKists. I was running out of fingers and buttons on my joypad... who-ever decided the thumbs should share both the analogue sticks and the buttons on the top? Anyway, I picked up a tilt-sensing joypad. Sadly proper tilt sensors are relatively expensive and games devices typically get made as cheaply as possible (grumble). To cut a long story short; it sends a fury of values that are somewhere around the value that it needs to be. Result; the poll-rate gets to be a kind of noisy harmonic. So; this leads to the question of how to interpolate this mess without making complex function calls at this high poll-rate and cook the poor CPU before we get any sound made at all. Solution; as soon as I get the value the axis moved to I write that to a Step Ugen's ".next()". Then; Step my_axis => LPF my_interpolation => blackhole; //set to taste, it's latency v.s. noise //maybe a rate that's relatively prime to the poll-rate would be best? 5 => my_interpolation.freq; then my_interpolation.last() can be polled at whatever rate makes sense. It can also be chucked directly to Ugens like oscillators set to act as a FM synth (use the filter's gain to scale) or to Gain's set to multiply. Very cheap and so far quite pleasant to work with, I thought I'd share. Yours, Kas.

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Future ChucK: wish list items and one comment
by Inventor-66＠comcast.net 02 Apr '08

02 Apr '08

Dear ChucKists, I look into my crystal ball and I see the future of ChucK, AKA my wish list: o MAUI ported to PC/Linux (on the way, woohoo!) o fix noteOff () problem o String Processing: preferably inspired by Perl o File I/O: I want to save and load program settings o printf (): formatted text/numeric output. o Hierarchical Events: i.e. event when any button in an array is pressed o MAUI Expansion: Text I/O, File Browser, 2D drawing, 3D drawing, etc. o Garbage Collection o Tube Amplifier UGen o Piano STK Instrument And there is one observation I'd like to share... Aside from it's musical capabilities, the one outstanding feature of ChucK to me is the way that everything works together. ChucK is very Apple/Linux-like in the way that it seems to be so well thought out. Of the dozen or two languages I've played with over the years, ChucK has got to be the most fun and the easiest to code because stuff just plain works. So my hat's off to the dev ChucKists, us user ChucKists are having a blast with your hard work! Inventor p.s. I went retro on the Pong game with the square ball as I remember from our Pong unit we had as kids, though I agree the LED would be way cooler. Maybe make it blink all three colors...

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