Straights vs curves
The contrast between straight lines and curved lines creates visual interest in any drawing. Lines and how they contrast is an essential design element. A sketch made up of straight lines would feel too tense, while a drawing using mostly curved lines would lack structure. When using these different lines in drawing a figure, curves are generally used to suggest the more fleshy part of the figure, whereas straights are more commonly used to imitate stable and solid segments. For example, compare the use of a straight line for a character’s back and on the soft curve of their stomach.