A novel approach is proposed that extends the classical background subtraction method to extract silhouettes from videos in real time with dynamic viewpoint variation caused by camera movement. First, manifold learning is used to model the background under viewpoint variations. Then, for each new frame, the background image corresponding to the same viewpoint is synthesized on the fly by examining the local neighborhood on the manifold, and the silhouette is extracted via background subtraction. An extension is also presented to generate stabilized silhouettes at any fixed viewpoint within the training range. Experiments show that our approach can efficiently extract accurate silhouettes in complex situations while maintaining a low noise level.