This was originally posted to the Anatomy Thread of Erich Schreiner, but I thought it would be generally useful to everyone:
Bringing all of the pieces together in figure drawing / painting is no easy / fast task, I sure haven’t mastered it. I think the key concept to bear in mind is that all forms, regardless of their complexity, are made of overlapping simple shapes.
You will see this concept repeated in all of representational figurative art throughout history. Well created form implies roundness from one side of the figure to the other. This is essentially the opposing curves concept in action. The white lines represent where the curve of one side of the organic shape implies the other side, and the black lines are the contour of the form which you intentionally create to bounce off of one another and to imply the other side:
Form created this way ‘breathes’. The invisible connections between the sides of the form give the sense of a flowing, organic, whole form. If one side of the form fails to imply the other, then the form looks flat and stiff, and doesn’t ‘breathe’.
This is why it helps to exxaggerate the roundness of form on the page. With only lines as visual cues to form, this opposing curves method is the essential ingredient to creating illusion of human form on the page.
Related information: Opposing Curves Article (Nudity)