1. A method comprising: obtaining video data depicting a head of a user; obtaining depth data associated with the video data; selecting seed pixels for a hair-identification flood fill for identifying pixels depicting hair of the head of the user, the seed pixels selected at least in part by using the obtained depth data; performing the hair-identification flood fill from the selected seed pixels, the hair-identification flood fill assigning respective distance-cost values to pixels of the video data based on respective position-space-cost values and respective color-space-cost values, wherein performing the hair-identification flood fill comprises: identifying a plurality of neighbor pixels of a current pixel; determining respective step-cost values from the current pixel to each pixel in the plurality of neighbor pixels; and assigning each pixel in the plurality of neighbor pixels a respective distance-cost value based on a distance-cost value of the current pixel and the respective step-cost values; and identifying, using a foreground identification process, a persona of the user from the video data, wherein the respective distance-cost values assigned to pixels by the hair-identification flood fill is one of a plurality of inputs of the foreground identification process.