1. A head mounted display (HMD) comprising: a display element configured to display content to a user wearing the HMD; an optics block configured to direct light from the display element to an exit pupil of the HMD; a plurality of light sources positioned at discrete locations around the optics block, the plurality of light sources configured to illuminate portions of a face, inside the HMD, of the user; a facial sensor configured to capture one or more facial data of a portion of the face illuminated by one or more of the plurality of light sources; and a controller configured to: receive a plurality of captured facial data from the facial sensor; identify a plurality of surfaces of the portion of the face based at least in part on the plurality of captured facial data; retrieve a plurality of landmarks each indicating a position of a different feature of the face, the plurality of landmarks determined based on calibration attributes corresponding to a plurality of different facial expressions performed by the user for a calibration process; map the plurality of surfaces to one of the plurality of landmarks; and generate facial animation information describing the portion of the face of the user based at least in part on the plurality of captured facial data and the mapping.