Let a=b, for values 1, 2, and 3:

Well, I'm not quite sure how to explain this, however, I will conjecture that the cases of a<b and a>b will be similar, except for their elliptical shape.

Let a<b, for values 1, 2, 3, and 4:

Let a>b, for values 1, 2, 3, and 4: