What are the classifications of sketches? It needs to be divided according to various situations.

There are realistic sketches and formal intention sketches. From the Renaissance to the end of 19, many generations of artists have exerted this ability to the extreme. Formal intention sketch requires us to learn what we want to draw rather than what we want to draw on the basis of certain realism and modeling ability. In other words, realistic sketch provides us with the ability to express nature, while intentional sketch satisfies our desire for free expression. What the modernist movement at the beginning of this century is keen on and perfect is the creation and discovery in the field of intentional sketch!