Results:

As I changed the value of N, coefficient of Theta, from 2 to 10 in the equation below, the initial structure of circle evolves into polygons with number of sides equal to the value of the coefficient(N).

Videos of evolution:

The following are the videos showcasing the evolution process for N=2,N=8,N=3

These are the various other structures obtained for values of N ranging from 2 to 10.The first picture is the initial shape of every grain before it evolves into following structures for successive values of N

Replacing Cosine in the above equation by Sine, for N=6 we get a hexagon which is tilted with respect to the hexagon which we obtain for the given equation which has cosine term i.e.The figure is shown below.

The same trend is observed for all the other cases too.