Game Development Reference
In-Depth Information
Traders
Traders
are nodes that cause resources to change ownership when fired: Two players
could use a trader to exchange resources. Machinations diagrams represent a trader
as a vertical line over two triangles that point left and right (
Figure 5.22
). Use trad-
ers when a given number of resources of one type is
exchanged for
(not converted
into) a given number of another type. This is ideal for any situation that resembles
shopping: the merchant receives money, and the customer receives goods in a stated
proportion (the price). If either the merchant or the customer does not have the
necessary resources, the trade cannot take place.
Fallout 3
, in which all traders' sup-
plies are limited, is a good example. A trading mechanism can be constructed by
two gates connected by a trigger ensuring that when one resource is received, the
other is returned in exchange.
FIGURe 5.22
Traders
NOTE
This is an
example of a color-
coded diagram, which
uses color to repre-
sent different kinds of
resources. in Figure
5.22, think of red as
representing money
and blue as repre-
senting goods. When
the interactive Trader
icon is clicked, three
money resources are
exchanged for two
goods resources. We
explain color-coded
diagrams in more detail
in chapter 6.
conVerters Vs. traders
From the perspective of a player, converters and traders have almost the same function:
Pass a number of resources to it and get a number of other resources in return. From
the
designer's
perspective, however, they are definitely not the same. The difference be-
comes clear from looking at their equivalent constructions in a machinations diagram. a
converter is a combination of a drain and a source. When activating a converter, resourc-
es are actually consumed and produced, and therefore the total number of resources in
the game might change. in contrast, activating a trader leads only to an exchange; the
number of resources in the game always stays the same.
end Conditions
Games end when certain conditions are fulfilled. Sometimes they end when a
player reaches a certain goal or when time runs out or when all players but one
are eliminated. Machinations diagrams use
end conditions
to specify end states. The
Machinations Tool checks the end conditions in a diagram at each time step and
stops running immediately when any end condition is fulfilled. End conditions are
square nodes with a smaller, filled square inside (the same symbol that is used to
indicate the stop button on most audio and video players). End conditions must
be activated by an activator. The activators are used to specify the end state of the
