IBSEN: Director-Actor Agent Collaboration for Controllable and Interactive Drama Script Generation

Abstract

Large language models have demonstrated their capabilities in storyline creation and human-like character role-playing. Current language model agents mainly focus on reasonable behaviors from the level of individuals, and their behaviors might be hard to constraint on the level of the whole storyline. In this paper we introduce IBSEN, a director-actor coordinate agent framework that generates drama scripts and makes the plot played by agents more controllable. The director agent writes plot outlines that the user desires to see, instructs the actor agents to role-play their characters, and reschedules the plot when human players participate in the scenario to ensure the plot is progressing towards the objective. To evaluate the framework, we create a novel drama plot that involves several actor agents and check the interactions between them under the instruction of the director agent. Evaluation results show that our framework could generate complete, diverse drama scripts from only a rough outline of plot objectives, meanwhile maintaining the characteristics of characters in the drama.

The implementation of the IBSEN framework is largely prompt-based, and one can easily construct IBSEN agents on any publicly available general LLMs without fine-tuning. We test and evaluate IBSEN in a drama scenario, meanwhile its framework design could be expanded to broader application cases, especially agent-based interactive games that contain specialized plot objectives. Demo video above shows a simple interactive surface implemented by RPG Maker MZ.

Agent Architecture

Director Agent - The central component of IBSEN, drives the whole storyline towards expected plot objectives.

• Read the script settings, get predefined plot objectives $\langle G_1, G_2, \dots\rangle$
• Write a continuation story outline $S_G$ that adheres to the current $G$
• Translate the outline $S_G$ into detailed dialogue scripts $\langle\hat{T}_1, \hat{T}_2, \dots\rangle_G$
• For each turn $\hat{T}=(r, \hat{u})$, generate instruction $I=\left\{S_G, Synopsis(\hat{u}), keywords\right\}$ to hint the actor role $r$ how to respond $u$ that fits the storyline and the character
• Check whether current objective $G_i$ is completed using the actual dialogue history $\langle\dots,T_{j-1},T_j\rangle$; move to the next objective $G_{i+1}$ if completed, otherwise still use the turn $\hat{T}_{j+1}$ generated before

Actor Agent - The distributed component of IBSEN, specifically modified to better suit the drama role-playing scenario.

• Maintain three databases: Actor Profile $D_P$, Memory Database $D_M$ and Character Database $D_C$ to store different categories of contents
• Use a first-person narrative monologue to interpret the content stored in the databases from the perspective and voice of the role-playing character
• Maintain a dialogue log $L=\langle T_1, T_2, \dots\rangle$ as the short-term memory; earlier dialogue turns will be gradually stored into databases for further retrieval
• Generate the response utterance $u$ using: role characteristics from $D_P$, related top memories from $D_M$, character impressions from $D_C$, instruction $I$ from director, script background and dialogue history from $L$

Director-Actor-Player Collaboration

IBSEN also allows human players to participate in the plot and interact with other characters. Though the player agent is controlled by humans, it can be seen as an actor agent that is not controlled by the director, and can take any action at any turn of the dialogue.

The director needs to dynamically adjust the plot to accommodate player actions while maintaining the development of the storyline:

• If no player involvement, still develop the storyline according to the dialogue script generated before
• Otherwise, always re-generate the current storyline and dialogue scripts, unless the current plot objective is completed

Evaluations

We create a novel interactive drama adopted from Hedda Gabler for evaluation. Check here to see our drama story settings!

• Most of the time, IBSEN follows the route of plot objectives and generates proper storylines, while maintaining the characteristics in the dialogue.
• New storylines generated by director tend to actively interact with the player.
• Player involvement may influence the behaviors of actors and impact the plot.
• Some common faults occasionally arise: high repetition, too many narrations, overly positive in some negative events.
• The backbone LLM influences the quality and the moral tendency of the responses.

Discussion

The idea of "controllable plot generation" can be extended to broader scenarios besides traditional drama. One of the most notable application fields is interactive gaming. For example, in communication games like script role-playing and table RPG, human players need to communicate with NPCs or each other to achieve certain tasks. In IBSEN, both the game master and NPCs can be role-played by AI generative agents, providing players with flexible gaming experiences at any place or time. As a backend framework, IBSEN can also be implemented in more complicated environments like video games, where players can deeper immerse in human-like interactions with NPCs through audio-visual elements. You may take a try in this video-game interactive demo!

BibTex

@inproceedings{han-etal-2024-ibsen,
    title = "{IBSEN}: Director-Actor Agent Collaboration for Controllable and Interactive Drama Script Generation",
    author = "Han, Senyu  and
      Chen, Lu  and
      Lin, Li-Min  and
      Xu, Zhengshan  and
      Yu, Kai",
    booktitle = "Proceedings of the 62nd Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)",
    month = aug,
    year = "2024",
    address = "Bangkok, Thailand",
    publisher = "Association for Computational Linguistics",
    url = "https://aclanthology.org/2024.acl-long.88",
    pages = "1607--1619",
}

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