Computer Graphics Laboratory ETH Zurich


Evaluating the Authoring Complexity of Interactive Narratives with Interactive Behaviour Trees

M. Kapadia, F. Zünd, J. Falk, M. Marti, R. Sumner, M. Gross

Proceedings of Foundations of Digital Games (Pacific Grove, CA, USA, June 22-25, 2015), pp.


This paper evaluates the use of Behavior Trees (BT) for authoring compelling narrative experiences with free-form user interaction. We systematically study extensions to traditionally BT representations, which decouple the monitoring of user input, the narrative, and how the user may influence the story outcome -- referred to as Interactive Behavior Trees (IBT's). By quantitatively evaluating the authoring complexity of BT formalisms with traditional story graph representations, we show that IBT's better scale with the number of story arcs, and the degree and granularity of user input. Our theoretical estimate of authoring complexity is corroborated with a qualitative user study, which confirms that subjects take lesser time with reduced effort to author narratives using IBT's. The subjective difficulty of IBT's is also lower than traditional story graphs.


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