Conveying Real-time Ambivalent Feelings through Asymmetric Facial Expressions Junghyun Ahn 1 , St´ ephane Gobron 2 , Daniel Thalmann 3 , and Ronan Boulic 1 1 Immersive Interaction Group (IIG), EPFL, Switzerland 2 Institute of Information and Communication Systems (ISIC), HE-Arc, Switzerland 3 Institute of Media Innovation (IMI), NTU, Singapore Abstract. Achieving effective facial emotional expressivity within a real- time rendering constraint requests to leverage on all possible inspiration sources and especially from the observations of real individuals. One of them is the frequent asymmetry of facial expressions of emotions, which allows to express complex emotional feelings such as suspicion, smirk, and hidden emotion due to social conventions. To achieve such a higher degree of facial expression, we propose a new model for mapping emotions onto a small set of 1D Facial Part Actions (FPA)s that act on antagonist muscle groups or on individual head orientation degree of freedoms. The proposed linear model can automatically drive a large number of au- tonomous virtual humans or support the interactive design of complex facial expressions over time. Keywords: VAD emotional model, facial parameters, asymmetric facial expression, real-time application 1 Introduction This paper proposes a new model for mapping the expression of complex emo- tions onto a small set of 1D Facial Part Actions (FPA)s acting on antagonist muscle groups or on individual head orientation degree of freedoms. Targeted applications are those requiring reactive on the fly emotional feedback from au- tonomous characters, for individual interaction as well as for large scale inhab- ited and shared virtual environments. Therefore, our key motivation is to offer a real-time technique for synthesizing far beyond the six universal emotions [17] and the emotion corpus spanned by the Valence Arousal Dominance (VAD) emotion space [3, 33]. Indeed, we aim at also rendering those complex emotions resulting in very demonstrative expressions, often with facial asymmetry [35]. We distinguish two types of asymmetry in the expression of emotions. The first one is a systematic asymmetry that depends on the nature of basic emotions such as raising one eyebrow to indicate suspicion [13]. The second type of asym- metry results from the simultaneous combination of two basic emotions, one on each side of the face, when an individual is unsuccessfully trying to hide one emotion by another one, e.g. sadness by fainted joy induced by social conven- tions (this was described as the “false smile” in [20]). The asymmetry we address