Le 08/08/2017 à 09:32, Jean-Marie Adrien a écrit :
Le 7 août 2017 à 13:56, cyrille henry <c...@chnry.net> a écrit :
hello,
I had a look at a modalys-help.pd file. It appear that modalys is not
implemented as a pd abstraction, but as a compiled object. I may be wrong, but
I think this object use modalys file that define all material / shape /
exitator / etc. So it's quite useless without the full modalys software.
anyway, in order to add my piece of answer to the original question:
about 20 years ago I made my master degree about a bow / string interaction
using a fake motorized bow and a virtual string.
2 different strings where implemented :
-The 1st sting was made using virtual 1D mass, spring and damper in a linear
arrangement, just like a spacial discretisation of a real string. This result
of incorrect tuning of high harmonics of the virtual string (regarding a real
string)
-The 2nd string was made using something also named "modal synthesis" (but very different
from modalys) : it was "just" mass/spring/damper 1D resonator connected together, a bit
like the paper initially send in this thread.
Since modalys use matrices, I guess that it use more complex interaction
between elements than a simple spring/damper interaction like I use to do. This
result in being able to also simulate the shape of the vibrating structure.
There is a gap between mass spring modeling and modal synthesis with results
from the mathematical formalization of the vibration phenomenon : to be short,
modal synthesis shifts towards an « abstract » representation of vibrating
structures which is general and applies to any vibrating object, mechanical or
gas.
This formalization considers that a vibrating structure is a set of vibrating
modes which are associated to a vibration frequency and a mode deformation
shape.
You can also do something like that with mass/spring system, event if it was
not the primary goal of this simulation!
a single mass/spring can create a resonating mode. Multiple mass/spring mode
can be coupled in parallel to create complex system. This can gives good result
for 1D system (a string) where there is no energy transfer from 1 mode to an
other.
Any vibrating deformation is thus computed as the infinite sum of elementary
(modal) deformations. This applies obviously to mass/ spring, to strings and …
to anything more complex.
This formalization is well known in maths (since 200 years or so), and used in
the industry since 60 years or so (for vibrations in trains, boats or bridges,
means large vibrating structures too complex to model with finite elements),
but was at first used for sound synthesis at IRCAM at the end of the eighties
as far as i know.
The advantage of seeing things this way is that
- on one hand you process in time domain, which allows the computation of
natural transients in complex musical situations (things impossible or very
difficult with other sound synthesis methods). Means you compute the
displacement in time domain of significant points (eg contact points and sound
pickup points). To achieve this, you simply program gestures on exciters
structures, and you obtain the corresponding complex sound.
- on the other hand you keep an eye on the frequency domain which is very
important in the musical perspective, because freqs are part of the
formalization.
Lastly, because the formalization is general, you are not « structure and
device design dependent » like you’re are for instance with finite elements of
with klarplus strong, and , as a result, you can work and program in a general
abstract way, and use interpolation and dynamic evolution (mapping) of
vibrating structures on the fly.
Mathematically, this boils down in a matrix equation to be solved at sample
rate, (means matrix inversion) the dimension of the matrix depending on the
number of interactions between vibrating structures.
If the structure is stable, you invert the matrix once and that’s it. If things
change (vibrato), you invert the matrix each time step.
On the top of the software, you have vibrating structures (tubes / rods /
plates / strings / membranes etc…), software to produce modal data from
physical parameters (size, density etc) and a menu of excitation types (hit,
blow, air jet, reed, double reed, glue, etc..) which connect the vibrating
structures together (exciters such as hammers, bows and fingers being also
vibrating structures).
You pick up the multi channel sound where you want on the vibrating structures.
Making sound is then assembling structures, and driving exciters with gestures,
just like you manipulate your bow and left hand fingers on a violin.
I will try to find my PHD dissertation (it was saved on micro film !) which
explains all this with multiple details, and from which the Missing Link
publication is a short summary.
thanks, i'll be glad to read it.
cheers
c
Because the PHD stuff is kind of official, there is a good chance i can find
the text somewhere. Of course i do not have any sample of this text at home (i
have to search) and even less a pdf, the dissertation was typed on a VAX
mainframe connected to a Versatec with an archeological text editor whose name
i do not even remember (no-one remembers though … maybe Miller… what was the
name of the text editor ? :)
JM
Anyway, about 15 years ago I start the pmpd library (physical modelling for
pure data) that provide simple mass / spring / damper simulation. The pmpd~
object allow this kind of simulation at audio rate. There is an example of the
1st kind of string simulation. The 2nd string can also be implemented thanks to
this object, but I did not provide any example since I miss the way to tune the
model.
pmpd~ provide only simple interaction, so I don't use it any-more. I use the
pmpd object that is lot's more complex (but works only at data rate) and a
simple hack to compute audio data. There is also an example in the library
distribution.
if you are interested, you can try pmpd using apt-get or deken on linux. I know
that Nicolas Montgermont compile pmpd for osX, so a recent binary exist
somewhere. I have no idea about recent build for windows.
cheers
C
Le 06/08/2017 à 21:58, Jean-Marie Adrien a écrit :
would be great if it would be in pd abstractions !
everything is in the paper though, you are right, and the method is incredibly
powerful, so the project was in that time to control it with gestures data
bases and artificial intelligence and so on, all of this being existing now,
not speaking about multi channel sound diffusion etc.
I was disappointed when, after having developed the method at IRCAM, i
discovered (and had to pay for it though) some ten years ago the actual modalys
thing that was kind of retro engineered after i left IRCAM, from the big C++
initial software with was developed between 1984 and 89.
The math is not so complex, it is just a matrix equation incremented step by
step, and very straightforward and intuitive discontinuities in time domain
which correspond to straightforward updates of the matrix, resulting for
instance from contact between objects and other intuitive events.
If you simplify the maths, it will probably become more complex i’d say, and
you will probably hear it, because time domain sound synthesis is quite
sensitive.
On the same line, one advantage of modal synthesis is that you can achieve
impossible physical excitations on imaginary structures, and interpolate
between all this, having transient sounds and articulations, but even with the
full math though, you could hear in that case that you were sort of tearing the
equations, which corresponds to the fact that there is no existing physical
gesture which you could refer to when exploring impossible configurations.
Math simplification is what happened probably when the available pd modalys
software was achieved : i was disappointed by this tool and rarely use it.
Another application has been developed by Apple in Logic with the "sculpture »
plugin : it is very much main stream, they probably make money with it and Im still
poor. Bref.
I’d love the true vintage thing on pd now : it is just implementing a matrix
equation with updates conditions.
The point is that, thirty years later, i do not understand anymore a single
line in C++, although I’ve written many thousands of lines.
Hmm. I dont believe it myself, how is this even possible ? But i remember very
well the principles. Id be happy to help if i can anyway.
jm
Le 6 août 2017 à 16:50, Jesse Mejia <jme...@anestheticaudio.com> a écrit :
Yes - I mentioned Ircam's Modalys and that paper in my initial post. Because
modal synthesis is so well known, and well documented, I'm surprised there
isn't a similar (but free!) pd implementation. Something with abstractions
instead of externals would be great.
So let's make one. I know it's a bank of resonant bandpasses, but working out
their relationships based on the modal characteristics of physical shapes seems
to be key, and abstracting those relationships to friendly controls.
The math in the papers is a bit beyond me but it looks like it's all there. I
can't tell by looking at it if it's something that would be too hard/annoying
to do with vanilla.. or if it's describable in a less math heavy way.
Alex - newly compiled versions of the stk would be great! I tried and failed at
that about a year ago. But the faust implementations compile well from faust to
pd.
On Aug 6, 2017, at 3:24 AM, cyrille henry <c...@chnry.net> wrote:
:)
indeed and i had myself to _pay_ for it, which is something that probably illustrates the
"élégance à la française"
jm
I did not encourage piracy, but since pd patch can't be protected I guess that
an anonymous source could leak the files without any trouble.
cheers
c
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