Level of Detail Based Behavior Control for Virtual Characters
We take the idea of Level of Detail (LOD) from its traditional use in computer graphics and apply it to the behavior of virtual characters. We describe how our approach handles LOD determination and how we used it to reduce the simulation quality of multi
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Abstract. We take the idea of Level of Detail (LOD) from its traditional use in computer graphics and apply it to the behavior of virtual characters. We describe how our approach handles LOD determination and how we used it to reduce the simulation quality of multiple aspects of the characters’ behavior in an existing application.
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Introduction
Traditionally, Level of Detail (LOD) is a concept found in 3D graphics programming aiming at reducing the total amount of polygons in a scene and thus increasing the overall performance. To this end, for each 3D-Object in the scene, the distance from the camera to this object is taken into account. The further away an object is from the camera, the less important it becomes for the user and the fewer polygons are drawn for it, following the rationale that the human eye will not be able to tell the difference. Different LODs can be discrete and are switched at certain distance thresholds or they can be continuous and the number of polygons is updated dynamically. Recent research extends the idea of LOD to the simulation of the behavior of virtual characters, using the terms ”Simulation LOD” or ”LOD AI”. The general idea is to find uninteresting or unimportant characters in the scene and reduce the simulation quality of their behavior accordingly. When applying LOD to the behavior of characters in this manner, new questions arise regarding the definition and usage of the different LODs: Is distance from the camera still a viable method to determine LOD for a certain character? Or are there situations in which a character might be interesting enough to exhibit its complete behavior, regardless of the distance to the camera? Which aspects of the behavior simulation can be reduced and how? In this work we address the above questions and present our approach of an LOD-based behavior control system. We also report how we integrated and tested our system in an existing application, the Virtual Beer Garden. The Virtual Beer Garden is a Sims-like virtual environment where characters try to satisfy certain needs by interacting with each other or smart objects in the environment. The novelty of our approach lies in the wide range of reducible aspects of behavior and the fact that the behavior reduction is applied at execution time and not beforehand during behavior selection. J. Allbeck et al. (Eds.): IVA 2010, LNAI 6356, pp. 118–124, 2010. c Springer-Verlag Berlin Heidelberg 2010
Level of Detail Based Behavior Control for Virtual Characters
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Related Work
Table 1 shows an overview of previous work on ”Simulation LOD” or ”LOD AI”, as well as our approach. As can be seen from the table, with a wide range of reducible aspects of behavior, LOD determination based on distance and visibility and a rather large number of different LODs, our work focuses on a more flexible approach which is applicable to many different applications and scenarios. Table 1. Comparison of different LOD approaches LOD Number based on of LODs Chenney et al. potential 2 [1] visibility Authors
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