2 Generative art What is generative art?
PROCEDURAL
Generative art is related to the broader field of computer art. However, not all computer art is generative art (Boden, 2009). For example, in video games, web design or in Photoshop compositions the computer is used as a tool rather than as a generator. But there is at least one technique used in video games that qualifies as generative art: procedural modeling (Ebert, Musgrave, Peachey, Perlin & Worley, 2003). Procedural modeling involves rendering natural material such as marble, stone and wood with a mathematical algorithm instead of using photographs.
Generative art generally lacks a commercial or political motive. Many generative artists explore rule-based systems out of curiosity and for aesthetic or scientific pleasure, rather than as a means to express an opinion. In recent years, generative approaches are also being applied to more practical applications in the form of data visualization (Fry, 2008). For example, one approach to visualize a network of links between various web pages is to use the following rules: “web pages are represented as knots, links as lines” and “all knots repulse each other” but “lines act as springs that attract two knots”. This is a specific kind of particle system (see further). Such kind of data- driven generative art is often characterized by a volatile, dynamic nature: the work in its current form may only exist at this particular time. The form changes as new data becomes available or as multiple authors contribute new rules (e.g., crowdsourcing).
Generative art represents a method to create art (i.e., rule-based) rather than a consistent artistic style (Galanter, 2003). Style and medium can vary greatly. Some generative artists use computer graphics while others build music composition systems, swarm robots, installations with growing plants, and so on. This diversity does not mean that generative art has a lack of interest in form as such. On the contrary, Galanter (2012) remarks:
Generative art, and especially generative art that harnesses what we are learning from complexity science, is a unique opportunity to rehabilitate formalism in art. It presents form as anything but arbitrary. It presents beauty as the result of an understandable universe neutral to human social construction in a fair and unbiased way.
Galanter's description signals how generative art ties in with the scientific field, by taking an unbiased stance towards style.
2.1 Brief history
The term “generative art” has gained popularity over the last decade, with principal instigators such as the Processing6 open source community and Marius Watz’ Generator.x7 forum. To date, the most widely quoted definition of generative art is again offered by Galanter (2003):
Generative art refers to any art practice where the artist uses a system, such as a set of natural language rules, a computer program, a machine, or other procedural invention, which is set into motion with some degree of autonomy contributing to or resulting in a completed work of art.
In later work Galanter has further emphasized the aspect of autonomy. To qualify as generative art, he notes, a rule-based system must be well-defined and self-contained enough to operate autonomously (Galanter, 2008). This excludes a handmade drawing. But it includes ancient tiling patterns, where individual tiles are placed according to a symmetry-based algorithm, and for example Sol LeWitt’s combinatorial sculptures and wall drawings. In fact, LeWitt’s conceptual approach to art, where “the idea becomes a machine that makes the art” (LeWitt, 1967), was already well-established in the field of computer art some years before (Nake, 2010). Another example at the foundation of generative art is the graphic work of Escher (1960), exploring concepts such as self-reference (Prententoonstelling, 1956), recursion (Circle Limit III, 1959) and infinity (Waterfall, 1961). Since Escher’s work is mostly hand drawn it is not generative in the true sense, but his notebooks contain resourceful rule systems which he used for tessellation or tiling. For example, the fish in Circle Limit III are based on the Poincaré disk model for hyperbolic geometry, introduced to Escher by Coxeter (1979).
Figure 8. “Circle Limit” III and “Circle Limit III original sketch”. All M.C. Escher works © 2012 The M.C. Escher Company (NL).
All rights reserved. Used by permission. www.mcescher.com
Watz (2005) agrees with Galanter that generative art can be found throughout history, but he attributes the term specifically to computer-based work created since the 1960’s. This includes the Artificial Life systems discussed in chapter 1, for example Conway’s GAME OF LIFE and BOIDS.
Other milestones include the work on fractal geometry by Mandelbrot (1982), L-systems (Prusinkiewicz & Lindenmayer, 1990) and particle systems (Reeves, 1983).
6 http://processing.org/ 7 http://www.generatorx.no/
FRACTALS
A fractal is a mathematical description of a self-similar (i.e., recursive) shape, consisting of smaller versions of itself. Examples include snowflakes, fern leaves and coastlines. In the 1970’s Mandelbrot convincingly used computer graphics to illustrate and popularize the development of fractals. Today, fractals play an important role in procedural modeling of surface and terrain (Perlin, 1985). A variation of the fractal, the attractor, is also popular in generative art.
L-SYSTEMS
An L-system is a recursive rewriting system that can be used to model growth in plants. For example, algae growth can be described as (A !AB), (B ! A) where A is rewritten to AB, then ABA, ABAAB, ABAABABA, and so on. Note that the length of the consecutive strings also satisfies the Fibonacci sequence (1, 2, 3, 5, 8, ...). L-systems were developed by Lindenmayer concurrent with Mandelbrot’s computer-generated fractals. Today, they are widely used in computer games to render procedural plants8, trees, or even entire cities (Parish & Müller, 2001).