Reference:Bumps Pattern

The bumps pattern was originally designed only to be used as a normal pattern. It uses a very smooth, random noise function that creates the look of rolling hills when scaled large or a bumpy orange peel when scaled small. Usually the bumps are about 1 unit apart.

When used as a normal pattern, this pattern uses a specialized normal perturbation function. This means that the pattern cannot be used with normal_map, slope_map or wave type modifiers in a normal statement.

When used as a pigment pattern or texture pattern, the bumps pattern is identical to bozo or spotted and is similar to normal bumps but is not identical as are most normals when compared to pigments.

Note: The appearance of the bumps pattern depends on the noise generator used. The default type is 2. This may be changed using the noise_generator keyword. See the section Pattern Modifiers: noise_generator.

bumps pattern used as pigment and normal respectively