US Patent 9208608 Systems and methods for feature tracking

A computer-implemented method for processing, by a graphical processor unit (GPU), a plurality of images of a user. A plurality of features detected by the GPU in a first image of the plurality of images of the user is selected. Each selected feature includes one or more pixels. In a second image of the plurality of images of the user, a search is performed for the plurality of features selected in the first image. A variance is calculated, on the GPU, for each selected feature found in the second image. The variance indicates a degree to which a portion of the second image varies from a corresponding portion of the first image. The calculated variance is stored in a variance file.