Here’s an interesting new discovery and proposal from the labs of MIT: self-sculpting sand.
Essentially, the idea is a (perhaps limited) alternative mode of 3D-printing: simply place a small, model object into the “sandbox,” and the “sand” replicates a life-size version of the model. And all this occurs in a distributed, sporder-like fashion.
A heap of smart sand would be analogous to the rough block of stone that a sculptor begins with. The individual grains would pass messages back and forth and selectively attach to each other to form a three-dimensional object; the grains not necessary to build that object would simply fall away.
Assuming that I understand the computer science behind this, the key to this system (and what makes it a sporder), is an algorithm that distributes the intelligence and the processing power among millions of grains of “smart sand,” rather than establishing a central processing unit to micromanages each grain from above. This is the only way to achieve this complex wonder efficiently – otherwise it would require a gargantuan amount of resources to run.
The ruleset and mechanism that places the spontaneous construction in the hands of the “agents” is as follows:
According to Gilpin-author on the new paper, the grains first pass messages to each other to determine which have missing neighbors. (In the grid model, each square could have eight neighbors.) Grains with missing neighbors are in one of two places: the perimeter of the heap or the perimeter of the embedded shape.
Once the grains surrounding the embedded shape identify themselves, they simply pass messages to other grains a fixed distance away, which in turn identify themselves as defining the perimeter of the duplicate. If the duplicate is supposed to be 10 times the size of the original, each square surrounding the embedded shape will map to 10 squares of the duplicate’s perimeter. Once the perimeter of the duplicate is established, the grains outside it can disconnect from their neighbors.