To account for gross outliers in the facial features' detected locations, a robust model's fitting procedure can be employed instead of a simple projection by setting the robust flag to true. However, in practice, when using a decaying search window size (that is, as set in face_tracker_params::ssize), this is often unnecessary as gross outliers typically remain far from its corresponding point in the
projected shape, and will likely lie outside the search region of the next level of the fitting procedure. Thus, the rate at which the search region size is reduced acts as an incremental outlier rejection scheme.