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FireAutomataCellular automata - FireChristophe Le Page, François Bousquet (Cirad) This model illustrates how the principles of cellular automata are implemented in Cormas. The spatial entity of the model (the cell), named FireAutomata_Cell, can take four states: #fire (red); #tree (green); #ash (grey); #empty (white). The initial state of each cell of the spatial grid is either set to #tree with a probability p or to #empty with a probability 1-p. One cell is set on fire, and then the spreading of the fire, defined in the cell transition function, occurs. The transition function is the following: a cell being a tree at time t-1 will become on fire at time t if at least one of its 4 neighbours (North, East, South, West) is on fire at time t-1. The cells being on fire will become ash at the next timestep, the cells being ash will become empty at the next timestep.
The probability to observe a resteint fire is high if p is lower than 0.55, whereas when p is greater than 0.55, a global fire is likely to occur. This "percolation" threshold characterizes cellular automata which are representing diffusion processes. See also (if you enjoy movie !) the animation made from a 100 x 100 spatial grid (p = 0.58).
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