Geoscience Reference
In-Depth Information
(a)
(b)
(c)
(d)
FIGURE 2.6
Masked neighbourhoods: restrictions on development. (a) Displaced von Neumann.
(b) Sierpinski gasket. (c) Superblock layout. (d) Superblock layout with ρ = 0.5.
design estates of superblocks in the 1950s and 1960s, and its replication is reminiscent of the
kinds of residential layout seen in municipal housing. In fact, it would be a relatively simple mat-
ter to add some meta-transition rules which enable green space and appropriate road access to be
incorporated, thus providing reasonable simulations of the kind of geometry that actually exists.
We can of course apply all the automata we have introduced to these modified neighbourhoods,
including the 505 which we have not shown in the examples so far. In Figure 2.6d, for example,
we show how we can apply a probabilistic threshold to the neighbourhood of Figure 2.6c but this
time letting the automata wrap around the screen. This produces a more realistic pattern which
begins to suggest how these transition rules might be embodied as shape grammars and how
physical constraints on development might be introduced so that these automata can reproduce
real situations.
The last example in this section introduces an entirely new theme. So far, we have only consid-
ered growth - new development in which cells can be switched on. Now, we consider replacement or
redevelopment, in which developed cells which reach a certain
age
are first turned off - emptied of
development or demolished, thus entering the development process once again. This is much more
akin to how development actually takes place. Buildings age and are renewed or demolished; new
buildings are then built on the same sites. For any CA, we have a complete development history, and
thus we know the age or time at which the cell was first or last developed. What we can now do is
introduce an age limit parameter which when reached by any cell causes that cell to become vacant
and thus eligible for re- or new development.
In most of the simple examples so far, space has been synchronised with time, and development
(growth) has proceeded in waves or bands at increasing distances from the central seed site. If an
age threshold is introduced in any of the examples so far, then waves of development and rede-
velopment can be seen pulsing out from the central seed site as the automata are run indefinitely
