For some directions the surface breaks into two facets. Ripples are formed. The orientation for this simulation is marked green. The left diagram is a polar plot of the normal directions at the finite difference nodes. Each red dot represents one node.
Triangles represent the directions, squares the directions and rectangles the directions.
Notice the rippled surface and the clustering of the red dots in the polar diagram in an elongated region. Three facets - Hillocks Second a surface which breaks into three facets. The orientation for this simulation is marked green. The left diagram is a polar plot of the normal directions at the finite difference nodes. Each red dot represents one node.