: random component (w.r.t. *granularity*)

: harmonic component (w.r.t. *repetitiveness*)

: generalised evanescent component
(w.r.t *directionality*)

The random component can be written as :

is the 2D innovation which is a white noise with variance

The harmonic component is given by :

*C*_{p},*D*_{p}are mutually orthogonal random variables

The evanescent component can be expressed :