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The reconstruction of facial expressions in embodied systems:
new approaches to an old problem

Karl Grammer and Elisabeth Oberzaucher

ZIF Mitteilungen 2/2006. pp. 14-31

In this explorative work we have demonstrated that it seems to be possible to create control architecture for expression simulation on the basis of only two controlling variables – pleasure and arousal - which can generate highly complex and variable facial expressions. This architecture can easily be implemented under a variety of conditions. This approach provides a simple solution for the action expression problem in virtual agents and embodied systems.
The system can generate virtually endless combinations of AU activations and thus the expressive behaviour of such an agent will never become monotonous. This approach also shows that a radical bottom up approach in nonverbal behaviour research is feasible and generates convincing results. In regard to the construction of avatars and embodied systems in our view this is the only approach, which is able to solve the action expression problem.
Besides the finding that the control architecture is feasible we have also demonstrated, that even apparently contradicting emotion theories can be implemented under the same control architecture. For instance it should be possible to weigh action units according to emotional categorical arousal. This means that these action units would be shown preferably, according to the given emotional conditions. With this architecture it would be possible to let an avatar show emotions, which apparently contradict the context – i.e. crying under highly happy circumstances.

Arousal (left) and Pleasure (right) from our circumplexmodel for the reconstruction of facial expressions.


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