Waveguide Library

Intuitive simple waveguides synthesis with Pd

Author:	Winfried Ritsch
Contact:	[email protected]
Revision:	1.03 Waveguide for acre lib
Copyright:	GPL by winfried ritsch IEM, 2009+
git master:	https://git.iem.at/pd/acre-wg

Target of this Pure Data abstractions library is to provide an intuitive simple set of objects to patch physical models of real or fantasy sounding objects. Many of them are simplified in favor for more intuitive handling of waveguide elements and instruments and do not always strictly follow the waveguide theory. The theory of most of the algorithms are based on the wonderful online documents about waveguide synthesis from Julian O. Smith III [JOS] at CCRMA Standford University.

[JOS]

see https://ccrma.stanford.edu/~jos/wg.html, Center for Computer Research in Music and Acoustics (CCRMA), Stanford University

Some instruments are implemented as examples and provided to serve as a start for own instruments and experiments. The 'acre' systematic with directories as prefixes is used to organize them. (see general acre documentation in acre base modules 'docu/').

Within physical modeling, the more sophisticated the models are, the more expressive parameters are needed to handle them and mostly the more difficult is to play them. Therefore in some of the instruments, the parameters are simplified and combined to allow an easier intuitive playing and also values are mapped to a more intuitive wield ranges.

Installation

Needed libraries: acre base module, zexy, iemlib1, iemlib2, iemmatrix

libraries not installed in the system, can be copied to "libs/" (thus if checkout fresh it should be empty)

acre-base module acre starting with version 2.0 should be installed in the Pd-search path.

Install this library in your search path naming this directory wg. Do not set search path inside this library since objects are referred as wg/<object> in the patches and should not conflict with other namespaces.

A proposed way to install is, to name the library directory wg and place it or link it in the directory of the acre base libraries.

To install it: clone it via git, download it from http://puredata.info/ or download/install it via deken.

Objects

Most objects are explained in their patches. An overview is provided here:

wave:

wave/ctl wave/out~ wave/in~

waveguide as a double delay, forward and backward, organized in two objects, 'in~' and 'out~', in favour for more lucid Pd patches. A possibility for "order forcing" is provided, to control where the loopback delay, controlled with the blocksize, will be added.

The minimum delay time, and therefore high frequencies, is limited by the block size, so the blocksize in the example instruments are adjusted in the parent patch, if needed, with the switch~ object.

As a GUI 'ctl' can be used to show the delay-time, which is mostly driven by other controls.

mic:

mic/mix_ctl mic/mix_ds mic/mix~

mic/mix~ is used to extract a signal out of a waveguide at a certain position, adding the forward and backward waves.

port:

port/3_ctl port/split3~ port/split3_ds port/3-damp~ port/3~ port/split3~-help port/split3_ctl port/3-damp_ctl

Ports should be named "junctions" and are objects which have two or more ports to connect to a waveguides ins and outs or other signal source or sink.

Some special junctions, like with damping function are also collected here. Note: this could/should be expanded to port/2~, port/4~ and so on, but since they has not been needed and therefore tested until now are omitted.

excite:

excite/pluck~ excite/pluck_ctl excite/pluck_ds excite/burst~ excite/burst_ctl excite/burst_ds excite/bow~ excite/bow_ctl excite/bow_ds

Some signal generators to excite a waveguide feedback networks. They are best documented within the examples.

blow:

blow/noise~ blow/noise_ctl blow/noise_ds blow/pressure~ blow/pressure_ctl

blow a reed, where noise is combined with pressure, see clarinet. This is separated from 'excite', since it combines pressure with noise in a special way.

damp:

damp/decay~ damp/decay_ds damp/filt~ damp/filt_ds damp/simple~ damp/simple_ds damp/simple_ctl

Simple damping with low-pass and a high pass, which also to filter out the DC is combined in 'simple~'. DC filtering is mostly needed because of on feedback inaccuracies, which can accumulate DC easily, but can also influence the effect of non-linear excitation objects, so must be carefully added.

Use damp where simple damping in feedback loop is needed. Decay additional reduces/destroys energy in a loop, so ports reflection factors are influenced. Most parameters are scaled from 0..100 for easier control.

Note that any filter mostly adds additional frequency dependent delays and therefore needs correction for excat tuning of instruments.

filt:

filt/pipebell~ filt/pipebell_ctl filt/pipebell_ds

this group of objects are 'static' filter like cases, membranes, bellbipes, ...

reed:

reed/simple~

is a special non-linear feedback and injection of blow especially for reed instruments, see clarinet.

bow

bow/table_ds bow/table_ctl bow/table~

Bow junction, see in examples 'string/bowed'

shape:

shape/limit~ shape/limit_ctl shape/limit_ds

shape objects are used to influence excitation of a signal. Since they are mostly non-linear, energy preservation is an issue. The amp factor is used how intensive they are applied. As an example limit, limits the excitation (see split string).

limiter:

limiter/dsp~

Sometimes to master waveguide instruments limiter are needed. The standard limiter, crack limits the maximum signal value (-1..+1). It can be used for very long or infinitely sustains.

Note: A small delay of 9 samples is added for the limiter to work exactly. For physical limit see shape object.

adsr

adsr/unpack adsr/ctl adsr/ctl_200 adsr/adsr_ds adsr/drive adsr/ds adsr/pack adsr/vgen~

For playing instruments adsr comes handy. Here is one provided to be independent from other libraries.

init:

init/ctl init/bang

to reinitialize the waveguides and instruments. A secure initialization is important, since physical models easily can go crazy. It is recommended to use it also in your patch for a kind of reset.

data

data/songs/mid2qlist data/songs/noteon_timer_dropnoteoff

data for initialization and demos.

Examples

clarinet

simple clarinet waveguide instrument

simple clarinet waveguide instrument

clarinet/dsp~

dsp chain for the clarinet

clarinet/ctl

combined GUI for playing

clarinet/ds

data storage for the clarinet

clarinet/slap_and_breath

demo preset to play it, better use the blow objects with ADSR

strings and pipes

string

string/simple~ string/simple_ctl string/simple_ds

Simple Waveguide with damping, like a string or pipe

bowed

string/bowed~ string/bowed_ctl string/bowed_ds

Simple bowed string, without body, see figure:

limited

string/limited~ string/limited_ds string/limited_ctl

String limited with a shape object in comparison to bowed, simplier excitation is done.

overtone

string/overtone~ string/overtone_ctl string/overtone_ds

Experiment play overtones of a string/pipe

metal plate

plate

plate/plane_ds plate/plane~ plate/plane_ctl plate/plane_drive

A metal plane should be simulated using waveguides and 3-port scattering.

the structure are waveguides at sides and in diogonal, with simplified controls:

[3PortSJ: 1]-0-wg A---[ 3port: 2]
         | \           / |
in->     I  \         /  I <- in
         |   0       /   |
         0    \     /    |
         |     \   /     |
         |      \ /      |
      wg D      X      wg B
         |      / \      |
         |     /   \     |
         |   wg F   wh E |
         |   /       \   |
in->     I  /         \  I <- in
         | /           \ |
[3Port: 4] ---wg C--- [3Port: 3]

- with four inputs on I
- 3 mics: 0
- Damping is constant on junction outputs with low-pass.

3. GPL-3 by winfried ritsch see acre