A system (200, 400, 900, 1150) for generating a three-dimensional model of a face of a user, the system comprising: a head-mounted display configured to present virtual content to a user (210, 410); an inward-facing imaging system (462, 1160a, 1160b), wherein the inward-facing imaging system is configured to image at least a portion of the face of the user (210, 410) while the user is wearing the HMD; an inertial measurement unit (1170a, 1170b) associated with the HMD and configured to detect movements of the HMD; and a hardware processor programmed to: detect a trigger to initiate imaging of a face of the user, wherein the trigger comprises a movement detected by the IMU (1170a, 1170b) involving putting the HMD onto a head of the user (210, 410) or taking the HMD off of the head of the user; activate, in response to detecting the trigger, the inward-facing imaging system (462, 1160a, 1160b) to acquire images; detect a stopping condition for stopping the imaging based on data acquired from at least one of the IMU or the inward-facing imaging system; analyze the images acquired by the inward-facing imaging system with a stereo vision algorithm; and fuse the images to generate a face model of the user's face based at least partly on an output of the stereo vision algorithm. a head-mounted display configured to present virtual content to a user (210, 410); an inward-facing imaging system (462, 1160a, 1160b), wherein the inward-facing imaging system is configured to image at least a portion of the face of the user (210, 410) while the user is wearing the HMD; an inertial measurement unit (1170a, 1170b) associated with the HMD and configured to detect movements of the HMD; and a hardware processor programmed to: detect a trigger to initiate imaging of a face of the user, wherein the trigger comprises a movement detected by the IMU (1170a, 1170b) involving putting the HMD onto a head of the user (210, 410) or taking the HMD off of the head of the user; activate, in response to detecting the trigger, the inward-facing imaging system (462, 1160a, 1160b) to acquire images; detect a stopping condition for stopping the imaging based on data acquired from at least one of the IMU or the inward-facing imaging system; analyze the images acquired by the inward-facing imaging system with a stereo vision algorithm; and fuse the images to generate a face model of the user's face based at least partly on an output of the stereo vision algorithm. detect a trigger to initiate imaging of a face of the user, wherein the trigger comprises a movement detected by the IMU (1170a, 1170b) involving putting the HMD onto a head of the user (210, 410) or taking the HMD off of the head of the user; activate, in response to detecting the trigger, the inward-facing imaging system (462, 1160a, 1160b) to acquire images; detect a stopping condition for stopping the imaging based on data acquired from at least one of the IMU or the inward-facing imaging system; analyze the images acquired by the inward-facing imaging system with a stereo vision algorithm; and fuse the images to generate a face model of the user's face based at least partly on an output of the stereo vision algorithm.