[PD] physical modelling/general pd

[cyrille henry]

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 at virgin.net>
>> Subject: [PD] physical modelling/general pd - mentor/tuition sought
>> (money offered)
>> To: <pd-list at iem.at>
>> Message-ID: <000001c8f881$0d514a40$27f3dec0$@brooks at 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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