in developing the image, some artists focus on the shapes created by the interplay of light and dark values on the surfaces of the body. others take an anatomical approach, beginning by approximating the internal skeleton of the figure, overlaying the internal organs and musculature, and covering those shapes with the skin, and finally (if applicable) clothing; study of human internal anatomy is usually involved in this technique. another approach is to loosely construct the body out of geometric shapes, e.g., a sphere for the cranium, a cylinder for the torso, etc. then refine those shapes to more closely resemble the human form.