L2Ork version of Pure-Data real-time digital signal processing language developed and maintained at DISIS, Virginia Tech
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maintainer: Ivica Ico Bukvic ico@vt.edu

maintainer: Jonathan Wilkes jancsika@yahoo.com

maintainer: Albert Graef aggraef@gmail.com

One Paragraph Overview

Pure Data (aka Pd) is a visual programming environment. That means you can use it to create software graphically by drawing diagrams instead of writing lines of code. These diagrams show how data flows through the software, displaying on the screen what text-based languages require you to piece together in your mind.

Distributions of Pure Data

There are currently three main distributions of Pure Data:

  1. Pd-L2Ork. Version used by Ivica Bukvic for his laptop orchestra. This guide is for Pd-L2Ork.
  2. Pure Data "Vanilla". Miller Puckette's personal version which he hosts on his website and maintains. It doesn't include external libraries like objects for doing graphics, video, etc.
  3. Pure Data Extended. A monolithic distribution which ships with lots of external libraries. At the moment it doesn't look to be maintained.

Three Paragraph Overview

Pd has been designed with an emphasis on generating sound, video, 2D/3D graphics, and connecting through sensors, input devices, and MIDI as well as OSC devices.

Pd has a special emphasis on generating audio and/or video in real time, with low latency. Much of its design focuses on receiving, manipulating, and delivering high-quality audio signals. Specifically, the software addresses the problem of how to do this efficiently and reliably on general purpose operating systems like OSX, Windows, Debian, etc.-- i.e., systems designed mainly for multi-tasking.

Pd can easily work over local and remote networks. It can be used to integrate wearable technology, motor systems, lighting rigs, and other equipment. Pd is also suitable for learning basic multimedia processing and visual programming methods, as well as for realizing complex systems for large-scale projects.

Pd-L2Ork Goals

Pd-L2Ork has the following goals:

  1. Documentation. We like documentation. It's like code, except friendly.
  2. Be reliable. Binary releases must be usable for performances and installations. The git repo must always be in a workable state that can be compiled. Regressions must be fixed quickly.
  3. Be discoverable. Undocumented features are buggy. Missing help files are bugs. Patches for new functionality that lack documentation are spam.
  4. Be consistent. Consistent interfaces are themselves a kind of documentation. We like documentation, so it follows that we like consistent interfaces.

Installation Guide

To install using a pre-compiled binary, follow these instructions: http://l2ork.music.vt.edu/main/?page_id=56

To set up a development environment, first make sure you have the following package dependencies listed here: http://l2ork.music.vt.edu/main/?page_id=56

Then follow the steps outlined here: http://l2ork.music.vt.edu/main/?page_id=56#install-dev

Contributor's Guide

Contributing is easy:

  1. Join the development list: http://disis.music.vt.edu/cgi-bin/mailman/listinfo/l2ork-dev
  2. Tell us what you'd like to work on. Unfortunately there are lots of externals and even core features that are poorly documented. We can help make sure you aren't duplicating functionality (or that you at least know what's already been implemented).
  3. Send us your patch and we'll try it out. If it's well-documented and there aren't any bugs we'll add it to the software.
  4. If you want to do regular development and have commit access, just request it, then follow the Pd-L2Ork goals above.

Here are some of the current tasks:

  • coming up with a better name than Pd-L2Ork. :)
    • skills needed: creativity, basic knowledge about programming in Pd
    • status: no work done on this yet
  • writing small audio/visual Pd games or demos to include in the next release
    • skills needed: ability to write Pd programs
    • status: I wrote a little sprite-based game that will ship with the next version of Pd-L2Ork. In it, the character walks around in an actual Pd diagram shoots at the objects to progress, and to make realtime changes to the music. What I'd like is to include a new, smallish game with each release that has a link in the Pd console. It can be a little demo or game, just something fun that shows off what can be done using Pure Data.
  • porting Pd-L2Ork's graphical user interface from Tcl/Tk to Qt.
    • skills needed: knowledge about Qt5/QML, threading, and Pd's core design and deterministic message-dispatching and scheduling
    • status: under active development
  • designing/implementing regression test template

Project "Underview" (Implementation and Code Style)

The following is adapted from Pd Vanilla's original source notes. (Found in pd/src/CHANGELOG.txt for some reason...)

Sections 2-3 below are quite old. Someone needs to check whether they even hold true for Pd Vanilla any more.

Structure definition roadmap.

First, the containment tree of things that can be sent messages ("pure data"). (note that t_object and t_text, and t_graph and t_canvas, should be unified...)

BEFORE 0.35:

m_pd.h	    t_pd    	    	    anything with a class
                t_gobj	    	    "graphic object"
                    t_text  	    text object
                    t_glist 	    list of graphic objects
g_canvas.c  	    	t_canvas    Pd "document"

AFTER 0.35:

m_pd.h	    t_pd    	    	    anything with a class
                t_gobj	    	    "graphic object"
                    t_text  	    patchable object, AKA t_object
g_canvas.h     	    	t_glist     list of graphic objects, AKA t_canvas

Other structures:

g_canvas.h  t_selection -- linked list of gobjs
            t_editor -- editor state, allocated for visible glists
m_imp.h     t_methodentry -- method handler
            t_widgetbehavior -- class-dependent editing behavior for gobjs
            t_parentwidgetbehavior -- objects' behavior on parent window
            t_class -- method definitions, instance size, flags, etc.

1. Coding Style

1.0 C coding style. The source should pass most "warnings" of C compilers (-Wall on linux, for instance; see the makefile.) Some informalities are intentional, for instance the loose use of function prototypes (see below) and uncast conversions from longer to shorter numerical formats. The code doesn't respect "const" yet.

1.1. Prefixes in structure elements. The names of structure elements always have a K&R-style prefix, as in ((t_atom)x)->a_type, where the "a_" prefix indicates "atom." This is intended to enhance readability (although the convention arose from a limitation of early C compilers.) Common prefixes are "w_" (word), "a_" (atom), "s_" (symbol), "ob_" (object), "te_" (text object), "g_" (graphical object), and "gl_" (glist, a list of graphical objects). Also, global symbols sometimes get prefixes, as in "s_float" (the symbol whose string is "float). Typedefs are prefixed by "t_". Most private structures, i.e., structures whose definitions appear in a ".c" file, are prefixed by "x_".

1.2. Function arguments. Many functions take as their first argument a pointer named "x", which is a pointer to a structure suggested by the function prefix; e.g., canvas_dirty(x, n) where "x" points to a canvas (t_canvas *x).

1.3. Function Prototypes. Functions which are used in at least two different files (besides where they originate) are prototyped in the appropriate include file. Functions which are provided in one file and used in one other are prototyped right where they are used. This is just to keep the size of the ".h" files down for readability's sake.

1.4. Whacko private terminology. Some terms are lifted from other historically relevant programs, notably "ugen" (which is just a tilde object; see d_ugen.c.)

1.5. Spacing. Tabs are 8 spaces; indentation is 4 spaces. Indenting curly brackets are by themselves on their own lines, as in:

if (x)
x = 0;

Lines should fit within 80 spaces.

2. Compatibility with Max

2.0. Max patch-level compatibility. "Import" and "Export" functions are provided which aspire to strict compatibility with 0.26 patches (ISPW version), but which don't get anywhere close to that yet. Where possible, features appearing on the Mac will someday also be provided; for instance, the connect message on the Mac offers segmented patch cords; these will devolve into straight lines in Pd. Many, many UI objects in Opcode Max will not appear in Pd, at least at first.

3. Source-level Compatibility with Max

3.0. Compatibility with Max 0.26 "externs"-- source-level compatibility. Pd objects follow the style of 0.26 objects as closely as possible, making exceptions in cases where the 0.26 model is clearly deficient. These are:

3.1. Anything involving the MacIntosh "Handle" data type is changed to use char * or void * instead.

3.2. Pd passes true single-precision floating-point arguments to methods; Max uses double. Typedefs are provided: t_floatarg, t_intarg for arguments passed by the message system t_float, t_int for the "word" union (in atoms, for example.)

3.3. Badly-named entities got name changes:

w_long --> w_int (in the "union word" structure)

3.4. Many library functions are renamed and have different arguments; I hope to provide an include file to alias them when compiling Max externs.

4. Function name prefixes

4.0. Function name prefixes. Many function names have prefixes which indicate what "package" they belong to. The exceptions are:

typedmess, vmess, getfn, gensym (m_class.c)
getbytes, freebytes, resizebytes (m_memory.c)
post, error, bug (s_print.c)

which are all frequently called and which don't fit into simple categories. Important packages are: (pd-gui:) pdgui -- everything (pd:) pd -- functions common to all "pd" objects obj -- fuctions common to all "patchable" objects ala Max sys -- "system" level functions binbuf -- functions manipulating binbufs class -- functions manipulating classes (other) -- functions common to the named Pd class

5. Source file prefixes

5.0. Source file prefixes. PD: s system interface m message system g graphics stuff d DSP objects x control objects z other

PD-GUI: t TK front end