These images show a structure composed of cylinders. These cylinders have an erodable outer gray sheath, and a fixed central blue core. Two noise values are calculated at the surface of every point of every cylinder and subtracted from the radius of the outer sheath. If the modified radius is still larger than that of the inner core, the sheath is drawn at that modified radius. The magnitude of the noise values increases in the successive images, producing a greater erosion effect. Two noise values are used - one low frequency and deep representing large dents, and one high frequency and shallow representing small deformations. This produces a more realistic surface than if only one noise value was used.