1. A computer-implemented method comprising: obtaining a three-dimensional scan of a subject; generating a customized digital model including a set of blendshapes using the three-dimensional scan, each of one or more blendshapes of the set of blendshapes representing at least a portion of a characteristic of the subject; receiving input data of the subject, the input data including video data and depth data; tracking body deformations of the subject by fitting the input data using one or more of the blendshapes of the set; generating a refined linear model including one or more adaptive principal component analysis shapes, the refined linear model being generated by deforming the set of blendshapes onto the input data to obtain a deformed mesh and projecting the deformed mesh to a linear adaptive principal component analysis subspace; and fitting the refined linear model onto the input data using the one or more adaptive principal component analysis shapes.