Re: [PD] physical modelling/general pd

Hello Julian, I have done a wind chime there is 2-3 years ago with PD/GEM/PMPD. I
used PHP to get on the web the value of direction and force of wind
in differents cities in Europe. Here a link for a video without sound (i remove it from the export) : http://djrayban2.free.fr/Movie/windChime.mov ++

Jack

Le 8 août 08 à 12:16, cyrille henry a écrit :

hello,

Mark Sexton a écrit :

...

Hi Julian Building a physical model of a wind chime might be easier than you
think, if you use modal or banded waveguide approaches to physical modelling
rather than the brute force approach of pmpd.

pmpd aim to model the movement, not the sound. the hamer and the tube of a simple wind chime could be modeled with
about 10 masses. To create a physical model of the sound is very different. but you need both to model the wind chime.

Cyrille

...

If you think of the wind chimes should as stiff bars, banded
waveguides would be ideal and are much more computationally efficient to
implement than brute force approaches: a resonant filter and delay per mode you
want to synthesis. I'd recommend perhaps starting with a simple modal implementation using filters and build up from there. This paper
gives a good introduction: http://www.cs.ubc.ca/~kvdoel/publications/modalpaper.pdf

If you're not familiar with modal synthesis and banded waveguides
there's plenty of information online and Perry Cook's book gives a good
overview of a range of approaches to modelling. http://www.cs.princeton.edu/~prc/AKPetersBook.htm

Some starting hints if you want to go down this route:

1. Create an impulse: a buffer of noise or single sample impulse
2. Feed this into perhaps 5 band pass IIR filters with a very

narrow Q, these will provide your resonant modes for each chime. 3. The frequencies of these filters will probably be non-integer
multiples of the fundamental, eventually you can get these by analysing an
actual wind chime, but if you wanted to build a proof of concept now then
these are typical modes of an aluminium bar (you can find further modal
frequency ratios in the Csound manual): [1, 2.756, 5.423, 8.988, 13.448, 18.680] 4. Scale the outputs of each of the resonant filters as
appropriate, this should be straight forward once you've done an audio analysis of
your wind chime.

At this point you have a simple resonating model of a wind chime.

5. Perhaps replace the impulse: you can remove the resonant

components of your wind chime recording and this will leave you with the
original noise impulse. Using this to trigger your model should help improve
realism. 6. Create a banded waveguide version, by adding feedback delays
for each mode. (have a read of this paper and a look at Fig. 4): http://soundlab.cs.princeton.edu/publications/1999_icmc_bar.pdf

There's a few further tweaks and improvements that can be done, but something along these lines should give a good result, be fairly
easy to implement and run more efficiently than brute force.

Happy to chat more on or off list on the physical model side or
algorithmic composition side, but you may find it easier than you thought once
you get going.

All the best

Mark Sexton Senior Lecturer MSc Computational Sound University of Portsmouth

...

Message: 2 Date: Thu, 7 Aug 2008 12:30:51 +0100 From: "Julian Brooks" julian.brooks@virgin.net Subject: [PD] physical modelling/general pd - mentor/tuition sought (money offered) To: pd-list@iem.at Message-ID: <000001c8f881$0d514a40$27f3dec0$@brooks@virgin.net> Content-Type: text/plain; charset="us-ascii"

Hi all,

I have a 12 month project as part of a masters degree, where I
wish to build a physical model of a wind chime. I then want to use the
interface to play some of my indeterminate compositions. I was going to attempt it
for my undergraduate degree but realised that it was far too complex for
the available time that I had then.

I have been using pd for a few years now, list lurking, working
through basic examples, building simple tools, using other peoples
patches etc. But this is too complex for me to do on my own. At my uni there
isn't anyone with better skills than me and I don't know of any local fellow
patchers.

Now as a musician, when I need to up my skills, I will look to
find some lessons when I have got as far as I can on my own.

So here goes...

Is there anyone with an hour a week to spare who can offer some mentoring/tuition for what we can deem to be the 'going rate'. I
am more than happy to do this remotely/online, I'm sure there is a way we
can work it out. There would be full credit given of course.

Pmpd seems like the way to go with this. I have worked through the examples, and, although I have my eye on what examples I would
presume to be the best starting points, I'm struggling to get started. The
physical modelling is where I first need to start but there's loads of pd
stuff I would like to be able to work through with someone, so this could
be a (me love you)longtime regular small money earner, if anyone's
interested.

I am in Hebden Bridge, West Yorkshire, UK, by the way. Any
pd'ers local, give us a shout.

Best wishes to all,

Jb

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