The City and the City is a book about borders, about separation inside the body of the same city. It’s a book about the mental construction of a division between two cities that are actually the same one, but in the mind of the citizens are neatly separated and disconnected. It’s also a book about a murder, and due to that, about the complex thoughts connected with the search of the solution of this mystery of a death woman.
So, the two themes, which emerge from this book in terms of an inspiration for the search of a material behavior in nature, are:
- - The idea of the border itself, both as inside border and and outside one; the material logic associated with this are so the concepts of “membrane” and “skin”.
- - The complexity of the mental processes involved, that reminds to the study of complex neuronal networks and of the computational capabilities involved in the material behavior.
In order to find a material that can fit these two different characteristics, the attention must be driven more on the biological world that to the one of the inert materials. What is needed it’s a system defined by an articulated membrane, that works as a filter, able to perform some sort of computation and of “mental” process. Moreover, this system must be complex enough to show varied and interesting patterns of behavior over time, and simple enough in order to be observed and understood.
Material
"Slime Mold or Mould is a broad term describing protists that use spores to reproduce. Slime molds were formerly classified as fungi, but are no longer considered part of this kingdom. Their common name refers to part of some of these organisms' life cycle, where they can appear ad gelatinous slime." (Wikipedia)
These simple organisms, composed either of a single multi-nucleated cell or of a aggregation of different unicellular individuals, are always defined by the outer membrane and, despite they simplicity and their small dimension, they show a complex range of behaviors, ranging from environment sensing, to patterns recognition and networks optimization.
Between this group, one organism appears as particularly interesting: the plasmodium Physarum Polycephalum, a true unicellular slime mold that grows in shady and moist areas, avoiding light and feeding of the bacteria presents in the surrounding. This organism can grow really fast (up to 1cm/hour) and span up to many square meters, without ever losing its own integrity as single cell.
“Slime molds are no more than a bag of amoebae encased in a thin slime sheath, yet they manage to have various behaviors that are equal to those of animals who possess muscles and nerves with ganglia -- that is, simple brains.“ (John Tyler Bonner)
Behaviors
The movement of the Physarum is based on shuttle streaming, that means that is based on the movement of the protoplasm back and forth in the tube-like structure created in space. This pattern of movement is almost always regular, and is advocated as one of the main self-regulatory mechanisms of the organism itself.
The main characteristic of the behavior of the Physarum is its own ability of performing complex computations in different situations, always trying to find the most effective solution for the environmental problems that it faces. This ability allow the slime mold to sense the surrounding environment, creating and then optimizing complex networks of tubes in order to reach the different food sources, and even to balance between different nutrients in different times. Recent researches demonstrate that these simple organisms seem also able to some primitive form of memory, making previsions on the recurrence of regular events pattern over time.
Phisical Model
Magnetic fields have been chosen to try to reproduce the self-organization of the Physarum in a network of attractions and repulsions. The magnetic fields have been produced with self-made magnets, and the particle behavior of the slime have been approximated using iron filling. Unfortunately the experiment shows many differences from the processes that occur in the mold, mainly due to the omnidirectional diffusion of the magnetic fields, and for the directionality of the diffusion of the iron filling.
Digital Explorations
Between the different possible strategies to model the complex growth of the mold, we choose to use the agent-based modeling, both beacuse it seemed the best way to simulate the dynamics of the growth more than the patterns in themselves and beacuse it appeared as one of the most direct way to link this system of form production with some sort of behavior able to produce architectural systems.
A clear help in this choice come from the advices that we received form Jeff Jones, of the Institute of Unconventional Computing of Bristol, who is studyng this organism and the ways to reproduce it digitally for his PhD thesis.
“Furthermore, mastering the use of agent-based models to implement pattern forming processes is a necessary step with a view to designing distributed problem solving devices.“ (Eric Bonabeau)
The first test have been carried out in the direction of the simulation of a random growth of the structural pattern fo the mold based on swarming logic, and in particular on the Craig Reynolds' boids rules, as they have been coded by Jose Sanchez.
Strenght:
- Generally keeps the unity of the structure
- Simulates quite well the random growth
- Explores the whole space of search
Weakness:
- Relies more on parameters tuning than on coherent simulation
- It is complex to define optimisation functions
- Computationally quite expensive
The second script is still based on the same flocking algorithm, but improves that by adding a mesh able to keep track of the "chemoattractor" levels, that is a way of measuring the number of agents that have choos a location as part of their trail.
Stenght:
- Stores the growth trail as chemoattractant level
- Define a possible way to growth in 3 dimensions
- High degree of flexibility
Weakness:
- Still based on flocking simulation
- Chemoattractant values are not influencing the movement of agents
- Relies on scaling and limitation parameters
After this, in order to study the passage from random growth to network optimization, we added over the flocking simulation a physics engine, based on Toxiclibs, that we used to create a springs network between agents, that at certain points was then relaxed, causing the optimization of the network itself.
Strenght:
- Approximates simple patterns of optimized networks
- Allows the control of the process
Weakness:
- Breaks the unity
- Relaxation time too short to allow the emergence of complex patterns
- Based on springs not on convergence criteria
Finally, in order to explore the generation on more complex patterns and to use the chemoattractor levels to dinamically influence the emergence of networks, we starte to look into the complex world of ant algorithms, especially regarding the formation of foraging patterns in army ants colonies. In this fundamental for us have been the book Swarm Intelligence by Eric Bonabeau, Marco Dorigo and Guy Theraulaz.
Strenght:
- Records the chemoattractant trail and influences the movement of agents through it
- Based on scientific test
- Shows the emergence of complex optimized networks
Weakness
- Growth limited to two directions
- Relies on different optimisation system from slime mold
- Computationally expensive
Conclusions / Perspectives
The research we carried out give us a good knowledge and helped us to create digital tools useful for the next phase, when these systems of breeding of architectural form will be redirected and applied to a real environment and to a real program, in order to foster the emergence of new ways of occuping the space with architecture.
Our will for the next phases of the development of an architectural proposal is not to use these complex biological systems just to optimize a structure digitally in order to then build it as an inert element. We thrive for the creation of a real living architecture, able to mantain a continuous exchange of matter and energy between itself and the environment, abble to modify itself and adapt to the external and internal condition.
More then this, we want to investigate the construction of a new relationship between man and environment, in which the architecture becomes the medium to build a negotiation between the parts, more than a war between the human kind and the natural forces.
CodesInTheClouds design studio - prof. Liss C Werner
Dessau Institute of Architecture
Slime Mold team : Lila Panahi Kazemi, Andrea Rossi
