During operation, an electronic device may capture images using multiple image sensors having different fields of view and positions. Then, the electronic device may determine, based at least in part on an apparent size of an anatomical feature in the images (such as an interpupillary distance) and a predefined or predetermined size of the anatomical feature, absolute motion of at least a portion of the individual along a direction between at least the portion of the individual and the electronic device. Moreover, the electronic device may compute based at least in part on an estimated distance along the direction corresponding to the apparent size and the predefined or predetermined size and angular information associated with one or more objects in the images relative to the positions, absolute motion of at least the portion of the individual in a plane that is perpendicular to the direction.