Mathematical Framework

Figure 2.1: The flow of information though the system. Predictive feedback from the 3-D dynamic model becomes prior knowledge for the 2-D observations process. Predicted control allows for more sensible predictive feedback.

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The human body is a complex dynamic system, whose visual features are time-varying, noisy signals. Accurately tracking the state of such a system requires use of a recursive estimation framework, as illustrated in figure 2.1. The elements of the framework are the observation model relating noisy pixel-level features to the higher-level skeletal model and vice versa, the dynamic skeletal model, and a model of typical behaviors. We will first describe the dynamic and observation models, and then the behavior model.