warp weighted loom – dave's blog of art and programming

One of the main objectives of the weavecoding project is to provide a simulation of the warp weighted loom to use for demonstrations and exploration of ancient weaving techniques. Beyond the 4 shaft loom dyadic calculator we need to show the actual process of weaving to explain how the structures and patterns emerge. Weaving is very much a 3D process and these visualisations fail to show that well. It also needs to be able to be driven by the flotsam tangible livecoding hardware so running on a Raspberry Pi is another requirement.

I’ve decided to make use of the Jellyfish procedural renderer to build something fast and flexible enough, while remaining cross platform. Jellyfish is a lisp-like language which compiles to a vector processing virtual machine written in C++, and approaches speeds of native code (with no garbage collection) while remaining very creative to work with, similar to fluxus livecoding. Previously I’ve only used it for small experiments rather than production like this, so I’ve needed to tighten up the compiler quite a bit. One of the areas which needed work (along with function arguments which were coming out backwards!) were the conditional statements, which I removed and replaced with a single if. Here is the compiler code at the lowest level which emits all the instructions required:

;; compiler code to output a list of instructions for (if pred true-expr false-expr)
(define (emit-if x)
  (let ((tblock (emit-expr (caddr x))) ;; compile true expression to a block
        (fblock (emit-expr (cadddr x)))) ;; compile false expression to block
    (append
     (emit-expr (cadr x)) ;; predicate - returns true or false
     (emit (vector jmz (+ (length tblock) 2) 0)) ;; if false skip true block
     tblock
     (emit (vector jmr (+ (length fblock) 1) 0)) ;; skip false block
     fblock)))

Then I can implement cond (which is a list of different options to check rather than one) as a purely syntactic form with a pre-processor function to create a series of nested ifs before compiling them:

;; preprocessor to take a cond list and convert to nested ifs 
(define (preprocess-cond-to-if x)
  (define (_ l)
    (cond
      ((null? l) 0)          ;; a cond without an else returns 0 
      ((eq? (caar l) 'else)  ;; check for else clause to do
          (cons 'do (pre-process (cdr (car l)))))
      (else (list 'if (pre-process (caar l)) ;; build an if
          (cons 'do (pre-process (cdr (car l))))
                  (_ (cdr l)))))) ;; keep going
  (_ (cdr x))) ;; ignores the 'cond'

Here’s an example of the if in use in the loom simulation at the ‘top’ level – it gets the current weaving draft value for the weft and warp thread position and uses it to move the weft polygons forward or back (in the z) a tiny amount to show up on the correct side of the warp.

(define calc-weft-z
    (lambda ()
        (set! weft-count (+ weft-count 1))
        (set! weft-z
              (if (> (read-draft) 0.5)
                  (vector 0 0 0.01)
                  (vector 0 0 -0.01)))))

One of the reasons I’m writing about all these levels of representation is that they feel close to the multiple representations present in weaving from draft to heddle layout, lift plan, fabric structure and resulting pattern.

Last week the weavingcodes/codingweaves project started with a trip to Denmark, our first stop was the Centre for Textiles Research in Copenhagen where we presented the project and gathered as much feedback as possible right at the beginning. The CTR was introduced to us by Eva Andersson Strand, and is an interdisciplinary centre which focuses on the relationships between textiles, environment and society.

This long-view perspective of technology is critical for us, as we are dealing with a combination of thinking in the moment via livecoding and a history of technology dating back to the neolithic. This is a warp weighted loom, the focus of much of Ellen Harlizius-KlÃ¼ck’s research and the technology we are going to be using for the project.

Weights like this are widespread in the archaeological record for many cultures around the world, with the earliest ones around 5000 BC. Similarly – a post-it note including a handy cuneiform translation:

Alex talked about livecoding as a backwards step, removing the interface – thinking about it as an unravelling of technology. His introduction to Algorave led to many connections later when Giovanni Fanfani described the abstract rhythmic patterns of Homeric rhapsodic poetry. These were performed by citizens, in a collaborative and somewhat improvised manner – the structures they form musically and in language are potentially of interest as they seem to echo the logic of weaving pattern.

Ellen described her research into tacit knowledge of ancient Greek society – how weaving provided thinking styles and ordering concepts for the earliest forms of mathematics and science which is the basis for much of the weavingcodes project. One additional theme that has come up fairly consistently is cryptography – Flavia Carraro’s description of ‘The Grid in the decipherment of the Linear B writing system: a “paper-Ââ€loom”?’ was another addition to this area.

Emma Cocker talked about Peneolopeian time – constant weaving and unravelling as a subversive act, and the concept of the kairos, as a timely action – the name given to the point at which the weft is made when the warp ‘shed’ is provided, as well as a part of the warp weighted loom. Her input was to provide a broader view to our explorations (as coders, weavers and archaeologists all tend to get caught up in technical minutiae from time to time). From our discussions it was apparent that one of the strongest connections between livecoding and ‘weaving as thought’ is a subversion of a form of work that is considered by the dominant culture as entirely utilitarian.

Tag: warp weighted loom

3D warp weighted loom simulation

Unravelling technology in Copenhagen