to the three tier global motion estimation unit in fig3 but with the gradient descent unit using affine transformation model the affine transformation model tunes the translation parameter m 1 by comparing the coordinate of the pixels on the background object and the coordinate of the respected pixels on the prior sprite to generate a first parameter set m 2 including at least a scale parameter a shear parameter and a rotation parameter for a better understanding of the three types of parameters take a square object a shown in fig8 for example after the affine transformation which represents the effect similar to the parallel plane projection the square object a is turned into rhombus object a 1 shearing transformation is applied rectangular object a 2 scaling transformation is applied or an object a 3 showing rotational deformation the perspective transformation subunit 226 is utilized to compare the coordinate spaces of the pixels of the background object and the coordinate of the prior sprite so as to tune the first parameter set m 2 generated by the hierarchical affine transformation subunit 224 and generate a second parameter set m 3 including at least a tuned scale parameter a tuned shear parameter a tuned rotation parameter a tuned translation parameter and a perspective parameter representing depth variation the perspective transformation model not only represents all the transformation types the affine transformation model possesses but also represents the variation.