Fig. 2.

The complete bipartite graph for the tracking problem. Nodes (squares) denote particles in two consecutive images. Edges carry weights (the likelihood that a particle travels from the initial position x_i to the final position y^j) and Boolean variables [indicating whether the nodes i and j in the two images correspond to each other (σ = 1) or not (σ = 0]. Conflicts arise from the constraint that a valid assignment is a one-to-one mapping of the particles in the two images [expressed by the constraint C({σ}) in Eq. 1].