In this painting and the previous one, I worked on the folds of the drapery. I try to figure out some sort of formula I can apply in generating convincing drapery folds. I know many art teachers are against teaching "formula" in art. I agree with it absolutely. Mechanically applying "formula" in art without understanding can limits the artist's development. However, If you have studied, there is nothing wrong to summarize your approaches into some sort of "formula".