Character-based Storytelling with Literary Feelings

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The realisation of interactive narratives involves two key aspects:

The generation of narrative actions, and
Their dramatisation or staging by the characters.

However, emotions are also an important part of the narrative as its unfolding, supported by characters' actions, transmits emotions to the reader.

Whilst most Interactive Storytelling systems developed to date have relied on planning techniques to drive the story by generating a sequence of actions, they followed a task-based approach to story representation, which essentially "solve" the task to which the story is equated. One major limitation of this approach has been that it fails to incorporate characters psychology, and as a consequence important aesthetic aspects of the narrative cannot be easily captured by Interactive Storytelling.

In 2007, we introduced a new approach to Interactive Storytelling, which aimed at reconciling narrative actions with the characters' attributed psychology as stated in the narrative. Our long-term goal was to be able to explore Interactive Storytelling for those narrative genres which are based on the characters' psychology rather than solely on their actions. We used as a starting point the formalisation by Gustave Flaubert himself of his novel Madame Bovary [Flaubert, 1856], which includes a detailed account of characters' desires and feelings [Leclerc, Y. (1995). Plans et Scenarios de Madame Bovary. CNRS Edtions].

Within novels themselves, the psychology of characters is not usually described at a cognitive level, in terms of basic emotions, but tends to be intertwined with the literary presentation of the text. In other words, the psychology of its characters is represented within the narrative through their feelings. These feelings tend to form part of a finer-grained ontology than commonly described emotions, and depart from traditional emotional models, e.g. of Ekmanian emotions. These characters’ feelings are used by our emotional planner as part of the planning domain and are therefore at the heart of narrative representations.

Using such feelings for narrative representations would bring a new perspective for character-based IS:

Character's feelings would determine their actions,
Interactions between characters (determined by one character acting upon an another according to its own feelings) will modify and update their respective feelings creating narrative backbone based on feelings evolution, and
User intervention is similar in nature to an interaction between virtual characters, the user interaction being interpreted as the same type of communicative actions between characters which parsed within current narrative context (e.g. characters'feelings and expectations) would modify their respective feelings.

To support this research, we implemented several prototype systems (CharBovary, EmoEmma, Emma VR) which integrate a purpose-built AI system with a 3D visualisation engine, the Unreal Tournament™ engine, using UDP sockets to exchange control messages. The interactive storytelling engine is based on a multithreaded HSP Planner controlling each character independently. 3D animations are generated from the grounded actions produced by the planner.

Finally, this novel approach has been fully detailled in the PhD thesis - Emotional Planning for Character-based Interactive Storytelling.

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