Game Development Reference
In-Depth Information
Each of the circles in Figure 7.2 represents a branch point, and each arrow repre-
sents a branch, that is, the player's movement along a plot line to the next branch
point. The storytelling engine keeps track of the player's position in the story at
any given moment.
As you look at Figure 7.2, be sure to note the following:
The branch points don't always have the same number of branches leading away
from them. A story can branch in any number of directions at any given point.
The branches go down or sideways, but they never go back up again. The dia-
gram depicts the possible progress of a story, and stories always move forward in
time, never backward. In the course of playing a single game, the plot never follows
the same branch or passes through the same branch point twice. This enforces the
rule that stories must not contain identical repeating events and helps avoid the
risk of continuity errors, as discussed earlier.
Unlike branches on a real tree, different branches can merge; that is, different
plot lines can converge. Many branch points can be reached by more than one path.
The diagram depicts two possible endings that may be reached by different
paths. The complete diagram would show additional endings farther down.
The diagram shows only one start point, but in fact a story could have several
start points if the player made a key decision before the story actually began. The
player might select one of several different characters to be his avatar, and that
choice could determine where the story begins. Or the storytelling engine could
choose from among several designated start points at random just to make the
beginning different each time the player plays the game.
The branching story mechanism is the classic method for creating interactive stories
that give players lots of agency. Branching plot lines let you tell a story in which
the player's actions strongly affect the plot, and he can see the effect of his actions
if he plays the game more than once and makes different decisions the second
time through.
DISADVANTAGES OF THE BRANCHING STORY
Be aware of the following three serious disadvantages of the branching story mech-
anism before you decide to use that structure for your game's story.
Branching stories are extremely expensive to implement because each branch
and each branch point require their own content. In Figure 7.2, a player can experi-
ence at most six branch points in playing from the top to the bottom of the
figure—not very many. That represents six player choices or challenges. After six
choices—for example, to take the left fork of the road, to enter the building, to go
upstairs instead of down, to talk to the old woman, to accept a letter she offers, to
leave the room—the player has barely started the game. Yet even this simplified
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