Automatic Story Generation for Computer Role-Playing Games

Scripting the plot in a computer role-playing game requires a large number of scripts that are difficult to track and maintain. Game adventures often have simple plots, called subquests, that are independent from the main plot. Sub-quests are important, as they add value to the open-world appeal of the game, but they still have to be scripted. We have created a prototype of a tool that helps by automatically producing design pattern specifications for sub-quests. The specifications can be entered into an existing tool, called ScriptEase, to generate scripting code for Neverwinter Nights adventures, without doing any manual scripting. The sub-quest patterns produced are logically consistent, ensuring the story can be completed by the player. The sub-quests are also designed to produce a better story by having the author adjust the amount of interactivity between the sub-quests. The entire process is done with little input from the author. Scripting Sub-Quests With Patterns The plot in computer role-playing games (CRPGs) has become quite complex. It is common for CRPGs to have complex story lines that allow for multiple story-arcs. Plot in CRPGs also involves the player character (PC) interacting with multiple game objects over time. Examples of interaction include the PC having a conversation with a character, unlocking a door, or acquiring an item. All of these interactions must be scripted, requiring expensive programmer time. Often in CRPGs, a simple plot will occur that is independent of the main story line. These simple plots, called sub-quests, are usually included to give the player a sense of a vast open world with unlimited opportunities and are often optional. Sub-quests are of vital importance to CRPGs. In the most popular games, a player can choose to take a break from the main plot and perform an optional sub-quest at any time. Sub-quests greatly add to the breadth of choices in a CRPG and provide motivations for a player to explore the game world. This increases a player’s sense of customization and ownership of PCs. The influence of the player on the main plot is often constrained, as specific plot options Copyright c © 2006, American Association for Artificial Intelligence (www.aaai.org). All rights reserved. are necessary to keep the game on track. Without any subquests, the player will feel constrained in their ability to influence the story. With sub-quests, the player can makemore unconstrained choices, since the main plot is protected. Sub-quests are generally simple compared to the complexity of the main plot, but CRPGs will often have a large number of sub-quests. Several sub-quests that all have a small amount of complexity can exhibit connections among them and maintain recurring patterns. These recurring patterns provide a theme that increases motivation, excitement and a sense of importance to activities that would otherwise be meaningless in the game. An example sub-quest pattern is to retrieve an item. This involves the PC needing to retrieve an item for some purpose. Examples of the retrieve an item pattern include the PC being asked by a non-player character (NPC) to retrieve a stolen amulet, the PC encountering a locked door requiring that a key be retrieved to unlock it, and the PC needing to retrieve a gear in order for a machine to work. A pattern can be represented as a sequence of roles. Each role in the pattern is played by an object in the game other than the PC. A role also has an action associated with it. This action represents the interaction between the PC and the object associated with the role that must take place in order for the role to be fulfilled. Examples of roles are: reaching a specific point in a conversation with an NPC, unlocking a door, and acquiring an item. Figure 1 shows a sequence of roles for a sample retrieve an item pattern. Reach hear about stolen amulet dialog on Silk Acquire stolen amulet from Orc Shaman Reach return stolen amulet dialog on Silk Figure 1: An example retrieve an item pattern.