Game Development Reference
In-Depth Information
Label modifiers are frequently used to model different aspects of game behavior.
For example, a pool might be used to represent a player's accumulated property in a
game of Monopoly . The more property a player has, the more likely it is that player
will collect money from other players. This can be represented by the diagram in
Figure 5.12 . Note that in this case the exact value of the label modifier is unspeci-
fied; it indicates only that the effect on the random flow rate is positive. Also note
that many mechanics of Monopoly are omitted in this diagram—for example, the
diagram does not show how a player acquires property. You will find diagrams that
paint a more complete picture of Monopoly in Chapters 6 and 8.
NOTE Figure 5.12
is not meant to be
simulated in the
machinations Tool;
it only illustrates the
principle.
FIGURe 5.11
a label modifier affecting the flow rate
between two pools. at a given time
step, the flow from B to c is 3 + 2 times
the number of items in a.
FIGURe 5.12
in Monopoly the state of your property posi-
tively affects the chance other players' money
flows to you.
nOde mOdiFiers
Node modifiers connect two nodes. They enable changes in the state of one node
(its origin) to modify the number of resources in another node (the target node),
according to the node modifier's label ( M ). When the origin node changes, it influ-
ences the target node in the next time step. More than one origin node can modify
a target node. The formula for this is nearly identical to the formula used for label
modifiers:
NOTE notice that
node modifiers can
create and destroy
resources if their tar-
get is a pool. This
is all right for an
abstract resource such
as “threat level” but
is best avoided for
tangible and intan-
gible resources such
as “keys” or “health.”
To create and destroy
those kinds of
resources, use other
types of nodes called
sources and drains,
described later in this
chapter.
N t+1 = N t + ∑ (M × ∆S)
node modiFiers can create shortaGes
By using negative node modifiers or redistributing resources from a node that has posi-
tive input node modifiers, it becomes possible that the number of resources on a node
becomes negative. in this case, the negative number of resources indicates a shortage.
no resources can be pulled from a node that has a shortage, and resources that flow into
a node with a shortage are used to compensate for the shortage first.
 
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