Reference:Discontinuous Patterns
Some patterns are discontinuous, meaning their slope is infinite. These patterns are not suitable for use as object normals. These patterns work best with textures and media:
Note: The cells and crackle patterns are mixed cases in that they are discontinuous at their respective boundaries. However, there is no limit to the different number of values, in the range of 0 to 1, that they can generate. When using the solid keyword with the crackle pattern it becomes discontinuous. The pavement and tiling patterns are also discontinuous at their respective boundaries, while other portions ramp.