1. An apparatus for encoding a data stream representing a temporally varying graphics model, the data stream comprising a series of data portions with coordinate data defining the graphics model at different time instants, comprising: a first predictor for predicting coordinate data of a first data portion currently to be encoded, based on coordinate data of a second data portion preceding the first data portion currently to be encoded, in order to obtain predicted coordinate data for the first data portion; a first comparator for comparing the predicted coordinate data for the first data portion and the coordinate data for the first data portion, in order to obtain prediction error vectors for the first data portion currently to be encoded; a second predictor for predicting the prediction error vectors for the first data portion based on prediction error vectors already obtained, in order to obtain predicted prediction error vectors for the first data portion; a second comparator for comparing the predicted prediction error vectors for the first data portion and the prediction error vectors for the first data portion, in order to obtain prediction error vector differences for the first data portion; and a processor for processing the prediction error vector differences for the first data portion, in order to obtain part of an encoded data stream.