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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example involves 21 branch points and 35 different branches, each of which requires its own story content: gameplay and narrative material. If none of the branches merged again, there would be even more. This rapid growth in the number of branches is called the combinatorial explosion. (Combinatorics is the field of math- ematics that studies the number of possible combinations of a set of things—in this case, a set of branch points in a branching story.)
As a result, most modern games don’t actually include much branching, and they often include long periods during which the player plays but doesn’t change the story. Wing Commander, a space combat simulator, contained a branching story, but it branched only between missions, not during them. Eventually, the Wing Commander series abandoned branching storylines entirely because they proved to be too expensive.
■ Every critical event (those that affect the entire remainder of the plot) has to branch into its own unique section of the tree. Suppose a character can live or die at a particular branch point. If he dies, he must never be seen again, which means none of the plot lines from his death onward can include him. His death requires an entirely separate part of the tree that can never merge back into the rest—otherwise, he might reappear after the player knows that he’s dead. If this happens with two characters, the game requires four separate versions of the story:
a version in which both live; a version in which both die; a version in which A lives and B dies; and a version in which B lives and A dies. Again, the number of possible combinations explodes.
■ The player must play the game repeatedly if he wants to see all the content.
If the storyline branches based on how well the player meets the game’s challenges and he’s very successful, then the next time he plays he has to play badly on pur- pose in order to learn the dramatic consequences of his failure! A lot of players would consider this to be absurd. They paid a great deal of money for the content in the game, and the only way to see it all is to play badly part of the time. This fac- tor further contributed to the industry’s abandoning stories that branch frequently.
If you want to make a branching story, you will have to plan out the structure in the concept stage of design. You should not actually write the story at that point in the design process, but you won’t be able to plan a budget or schedule for your game unless you know how much content it will require, and a branching story’s resource requirements expand very rapidly.
If you find that these drawbacks discourage you from using a branching structure, you can choose the compromise that the game industry most often uses when it creates nonlinear stories today: the foldback story.
Foldback Stories
Foldback stories represent a compromise between branching stories and linear ones.
In a foldback story, the plot branches a number of times but eventually folds back to
ptg7947181 a single, inevitable event before branching again and folding back
again to another inevitable event. (These are also sometimes called multilinear stories.) This may happen several times before the end of the story. See Figure 7.3 for a simplified example. The Secret of Monkey Island follows this format, as do many of the traditional graphic adventure games.
Most foldback stories have one ending, as shown in the figure, but this isn’t a requirement. You can construct a foldback story that branches outward to multiple endings from its last inevitable event.
Foldback stories offer players agency but in more limited amounts.
The player believes that her decisions control the course of events, and they do at times, but she cannot avoid certain events no matter what she does. She may not notice this the first time that she plays and may think that the story reflects her own choices at all times. If she plays the game more than once, how- ever, she will suspect that some events are inevitable and that the apparent control she enjoyed on the first play-through was an illusion. This is not necessarily a bad thing and can be useful to you as a storyteller. There’s no reason why an interactive story must offer the player a way to avoid any event that she doesn’t want to experience. After all, stories have always included the occasional event that the protagonist can do nothing about. If Scarlett O’Hara could have prevented Atlanta from being burned in Gone with the Wind, the story would have had a very different outcome and lost much of its emotional power. It’s reasonable to use inevitable events to establish plot-critical situations that the player cannot reasonably expect to prevent or change.
The foldback story is the standard structure used by modern games to allow the player some agency without the cost and complexity of a branching story. Developers routinely construct the interactive stories in adventure games and role-playing games as foldback stories. Of all forms of nonlinear interactive storytelling, it is the easiest to devise and the most commercially successful.
If you want to create a foldback story, you should choose critical turning points in the plot to be the inevitable events. They need not always be large-scale events like the burning of Atlanta. They simply should be events that change things forever and from which there is no turning back. The hero facing his final challenge, for instance, or the death of an important character, both work well as inevitable FIGURE 7.3
Simplified structure of a foldback story
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events. Obi-Wan Kenobi’s death, in Star Wars IV: A New Hope, works well as an inev- itable event.
Emergent Narrative
Emergent narrative, a term introduced by designer Marc LeBlanc in his lecture
“Formal Design Tools” at the 2000 Game Developers’ Conference, refers to story- telling produced entirely by player actions and in-game events (LeBlanc, 2000).
Emergent narrative storytelling does not contain narrative blocks (which he calls embedded narrative) created by a writer. The story emerges from the act of playing.
There is no separate storytelling engine and no preplanned story structure, either linear or branching; in principle, anything can happen at any time so long as the core mechanics permit it.
Playing The Sims can create emergent narratives because the game simulates the activities of a group of characters and contains no prewritten narrative blocks.
However, The Sims is not really a device for telling stories to the player because it gives the player so much control that he doesn’t feel as if he’s interacting with a story but rather that he’s creating a story. The game is more of an authoring tool.
(See Chapter 5, “Creative and Expressive Play,” for further discussion of player sto- rytelling as a form of creative play.)
The chief benefit of emergent narrative is that the sequence of events is not fixed by a linear or branching structure, so the player enjoys more agency. He can bring about any situation that the core mechanics will let him create. However, the player can control the story’s events only to the extent that he can control the core mechanics through his play. If the designer sets up the core mechanics in such a way as to force a particular situation on the player, his experience can be just as restricted as in a foldback story.
LeBlanc himself points out that emergent narrative is not without its problems. For one thing, it requires that the core mechanics be able to automatically generate credible, coherent, and dramatically meaningful stories—an extremely tall order.
Core mechanics are defined in terms of mathematical relationships rather than human ones; how can they produce reasonable human behavior? How can you make them generate emotionally satisfying stories algorithmically? At the moment, with the field in its infancy, nobody knows. Furthermore, the core mechanics must limit repetition and randomness, and at the moment, the core mechanics of most games produce a lot of both. Finally, emergent narrative seems to offer nothing for conventionally trained writers to do, and it might not be wise to give up on ordi- nary writers just yet, given the millennia of storytelling experience they represent.
The best information available right now doesn’t reveal the existence of any com- mercial games that make use of purely emergent narrative without any embedded
—that is, prewritten—material. The industry does not yet have any software that generates stories good enough for commercial entertainment products. At the moment, emergent narrative remains an experimental technique, part of an AI research field known as automated storytelling, which offers great potential for the future.
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