Spiney membrane model This applet displays a cellular automaton model of membranes. The model is exactly reversible - and can be run backwards by ticking the checkbox supplied. It is a development of the "string" model - and uses the same neighbourhood and number of states per cell - but applies a different rule. As with the other membrane models here, it preserves volume, and topology. Partition rules The automaton can be thought of as consisting of three layers: Simple gas - used solely as a source of biased pseudo-random numbers (and not displayed); Diffusing gas - used to greate pressure between the membranes; Membrane cells - used to construct the membranes; Each partition is divided into sixteen cells. Each cell contains one of two states - depicted as: & Cellular evolution progresses according to a very large number of rules: If a bit in the gas PRNG layer is set the contents of the partition remain unchanged... ...otherwise the following transformations are applied: <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> <-> ...in all rotated, reflected and inverted variations. If the state of the partition is not in the list above, it remains unchanged. Some things to note about the rules: The 12 edge cells are never modified; The count of the number of cells is preserved; Spatial topology is preserved; Regions remain orthogonally connected at all times. Fractal structures appear to emerge during the evolution of the automaton. The resulting "spiney structures" are potentially mobile - but exhibit a powerful tendency to stay in one place.