In this paper, we describe an Augmented Reality Art installation, which reacts to user behaviour using Multimodal analysis of affective signals. The installation features a virtual tree, whose growth is influenced by the perceived emotional response from spectators. The system implements a 'magic mirror' paradigm (using a large-screen display or projection system) and is based on the ARToolkit with extended representations for scene graphs. The system relies on a PAD dimensional model of affect to support the fusion of different affective modalities, while also supporting the representation of affective responses that relate to aesthetic impressions. The influence of affective input on the visual component is achieved by mapping affective data to an L-System governing virtual tree behaviour. We have performed an early evaluation of the system, both from the technical perspective and in terms of user experience. Post-hoc questionnaires were generally consistent with data from multimodal affective processing, and users rated the overall experience as positive and enjoyable, regardless of how proactive they were in their interaction with the installation.

3D graphics systems increasingly rely on sophisticated event systems derived from collision detection mechanisms, which support the discretisation of Physics as well as high-level programming and scripting. By contrast, augmented reality systems have not yet adopted this approach. We describe the development of a high-level event system on top of the ARToolkit environment incorporating the ODE Physics engine. We first define a typology of events encompassing interactions between virtual objects as well as interactions involving markers. We then describe how these events can be recognised in real-time from elementary collisions detected by the ODE Physics engine. We conclude by discussing examples of high-level event recognitions and how they can support the development of applications.