Using multiple cues for hand tracking and model refinement

We present a model based approach to the integration of multiple cues for tracking high degree of freedom articulated motions and model refinement. We then apply it to the problem of hand tracking using a single camera sequence. Hand tracking is particularly challenging because of occlusions, shading variations, and the high dimensionality of the motion. The novelty of our approach is in the combination of multiple sources of information, which come from edges, optical flow, and shading information in order to refine the model during tracking. We first use a previously formulated generalized version of the gradient-based optical flow constraint, that includes shading flow i.e., the variation of the shading of the object as it rotates with respect to the light source. Using this model we track its complex articulated motion in the presence of shading changes. We use a forward recursive dynamic model to track the motion in response to data derived 3D forces applied to the model. However, due to inaccurate initial shape, the generalized optical flow constraint is violated. We use the error in the generalized optical flow equation to compute generalized forces that correct the model shape at each step. The effectiveness of our approach is demonstrated with experiments on a number of different hand motions with shading changes, rotations and occlusions of significant parts of the hand.