Gradation

It is too strict a discipline, it not only requires a gradual change, but that gradual change, done in an orderly manner. It generates an optical illusion and creates a sense of progression, which typically leads to a culmination or series of culminations. It is a daily visual experience. Things that are close to us seem big, and things that are far away seem small. If we look from below at a tall building, with a facade of equal windows, the change in size of the windows suggests a law of gradation.