Constructing a user's face model using particle filters is disclosed, including: using a first particle filter to generate a new plurality of sets of extrinsic camera information particles corresponding to respective ones of a plurality of images based at least in part on a selected face model particle; selecting a subset of the new plurality of sets of extrinsic camera information particles corresponding to respective ones of the plurality of images; and using a second particle filter to generate a new plurality of face model particles corresponding to the plurality of images based at least in part on the selected subset of the new plurality of sets of extrinsic camera information particles.