1. A computer-implemented method to retarget facial expressions by providing a parameter-parallel retargeting space between an input facial expression and an output facial expression and via a plurality of facial layers, the method comprising: receiving input representing a facial expression of a first character; generating a plurality of facial layers for the first character, based on the received input and by operation of one or more computer processors, wherein the plurality of facial layers includes one or more parameters extracted from the received input; and generating a facial expression for a second character and corresponding to the facial expression of the first character, based on the plurality of facial layers.