Game Development Reference
In-Depth Information
FIGURE 7.1
The relationship
between storytelling
engine, core mechan-
ics, and user interface
PLAYER
Outputs
Inputs
USER INTERFACE
Narrative Events
In-Game Events
Player Events
Triggers
STORYTELLING ENGINE
CORE MECHANICS
Notice that a double-headed arrow labeled Triggers connects the storytelling engine
to the core mechanics in Figure 7.1. At times, the core mechanics may determine
that the interaction should stop and the storytelling engine should present some
narrative—for instance, when a player completes a level. The core mechanics send a
message to the storytelling engine saying that the player finished the level and the
storytelling engine should now display any interlevel narrative events. Likewise,
the storytelling engine can send a trigger back to the core mechanics when a narra-
tive event finishes (or when the player interrupts a narrative event), telling the core
mechanics to resume play.
The storytelling engine doesn't sit idle during play, however. As the player pro-
gresses, the mechanics continually send triggers to the storytelling engine—that
way, the storytelling engine can keep up with what's going on. If, for example, the
player makes a key decision that will affect the story later on, the core mechanics
inform the storytelling engine of the decision.
Similarly, during play the storytelling engine can determine that the story has
reached a critical plot point and trigger the core mechanics to cause changes to the
internal economy of the game. Suppose the story says, “When the avatar reaches
the bridge, he will be attacked by a highwayman in a cut-scene and robbed of all
his property.” The core mechanics, tracking the player's progress through the game
world, send a message to the storytelling engine, “The avatar has reached the bridge.”
The storytelling engine detects that this is a key point, halts play, and displays a
cut-scene showing the robbery. Then it transmits a message back to the core mechan-
ics saying, “Transfer the avatar's inventory to the highwayman and resume play.”
Normally, the level designers do the work that actually implements such events in
the game. Among the level designer's tools for level-building will be a mechanism
