Generative art is often a balance between regularity and randomness.
If regularity is very easy to obtain with computers, randomness is a bit more difficult to master.
This pen illustrates an elementary technique used when raw random numbers give unsatisfying results. Here, we want to color a background with shades of grey.
Click to draw a new random pattern.
Raw random values are actually taken only in a few points (red dots). Intermediate values are obtained by a 3rd degree polynomial interpolation (3 - 2 * x) * x * x (red dashed line). Linear interpolation can work too, but the result is less soft.