Heavier lines suggest areas of the drawing that are closer, and lighter lines suggest distance. Straight lines can help emphasize an angled plane in drawings that have depth. Curved lines help accentuate areas that are contoured and rounded. Shading can be used to help define a three-dimensional appearance in objects such as a box, cylinder, or sphere. Lighting and shade are determined by the light source illuminating the subject.
Rounded objects become darker as the edges curve away from the viewer.
The shading for these areas can be created by using the flat side of your pencil and gradually darkening the edges as they recede. To help diffuse shaded areas, try rubbing the pencil lines until the area has a uniform tonal gradient. To suggest highlights within shaded areas, try using your eraser to lift out graphite or charcoal pigment. At the component level, most objects can be segmented into a series of smaller, overlapping objects. By first sketching the component parts of an object, a composite can be created that helps define proportion.