A Demonstration of ScriptEase Ambient and PC-Interactive Behavior Generation for Computer Role-Playing Games

ScriptEase is a visual tool that enables game designers to create complex interactive stories for computer role-playing games, without programming. In particular, ScriptEase automatically generates the scripting code for ambient and PC-interactive non-player character (NPC) behaviors from a set of behavior patterns. Without ScriptEase, a game designer would have to write scripting code manually to specify NPC behaviors. This demonstration describes the steps of generating complex and non-repetitive ambient and PC-interactive behavior scripts using generative behavior patterns with ScriptEase. We show how ambient behavior patterns are used to re-generate and improve the behaviors of all ambient NPCs in the Prelude module of the BioWare Corp.’s Neverwinter Nights official campaign. We also demonstrate PC-interactive behaviors for a guard NPC in a custom Neverwinter Nights game module. With ScriptEase behavior patterns, game designers can easily and quickly populate a story with an engaging group of NPCs. Interactive Character Behaviors Many non-player characters (NPCs) that could potentially enrich a game adventure display repetitive behaviors due to the difficulties that occur when trying to script interactions between them [3]. For example, in games such as Fable and Morrowind, the state-of-the-art character behaviors are repetitive, with characters that rarely interact with each other [1]. NPCs walk predefined paths, make random comments about the player character (PC), stand still or perform a simple animation. In Sims 2, ambient behaviors are more developed, but they are very dependent on the design model integral to the game. The most novel and challenging ambient behaviors are the ones that use behaviors collaboratively (interacting NPCs) and these are rarely seen in computer role-playing games (CRPGs). We have developed a mechanism that generates engaging NPC behaviors without writing code. Our ambient and PCinteractive behavior patterns generate complex and nonrepetitive NPC behaviors. A behavior pattern is defined by a set of behaviors and a three-fold control model that selects the most appropriate behavior at any given time. A Copyright © 2006, American Association for Artificial Intelligence. All rights reserved. behavior can be used proactively in a spontaneous manner or reactively in response to another behavior. This demonstration illustrates the coverage of our proactive/reactive models. We also support PC-interactive behaviors, where the PC’s actions affect NPC behaviors and we demonstrate a Guard to highlight our PCinteractive model. These behaviors are sufficiently interesting to assess the use of ScriptEase [5] behavior patterns for generating scripting code for NPC behaviors. An ambient behavior pattern generates two types of NPC behaviors. An independent behavior occurs when the NPC acts alone. If the NPC interacts with another NPC, its behavior is collaborative. We conducted a case study for the Prelude of Bioware Corp.’s Neverwinter Nights (NWN) campaign story directed at both independent and collaborative behaviors. Collaborative behaviors are rare in CRPGs because their existence complicates event synchronization. Halo 2 [2] has support for “joint behaviors” but the game designer still has to write custom code for these behaviors. We developed a concurrency control mechanism that solves the inherent synchronization problems [1]. An eye-contact mechanism prevents new ambient behaviors from being initiated while an NPC is still executing behaviors in progress or when a PCinteractive behavior occurs. The synchronization model used by ScriptEase behavior patterns is scalable to more complex character interactions. Our behavior pattern set can be generalized to cover the behaviors of NPCs in other settings, such as a tavern, commonly occurring in CRPGs. Ambient Behavior Patterns Each behavior pattern is composed of basic behaviors that are re-usable and easy to assemble together. The Duet ambient behavior pattern is used to simulate the behaviors of all interacting pairs of NPCs that take turns in accomplishing a collaborative task, such as the spellcasterspellcaster, spawner-destroyer, and speaker-speaker. To demonstrate the utility of our approach, we removed all of the manually scripted NPC behaviors in the Prelude of the NWN official campaign and we show a demonstration of a revised Prelude, where all NPC behaviors are generated from our patterns. We show that the resulting scene is much more entertaining than similar scenes in the original game module. As a result of this study, six new ambient