Rendering Mass

1. Continuous Surface Directional Line. It is eminently feasible to make use of line that continuously traces the angular or curvilinear expansiveness of surface--a line that seemingly comes into view from one side and disappears out of sight to the other can shape mass. A relatively simple process of closely tracing the external planes and curved surfaces of mass, on the one hand, and of its internal space volumes, on the other.

2. Continuous Surface Directional Tone. A graphic combination of tonal values. Light and shade--light to reflect from the nearer parts, and shadow to indicate the underneath, other side, or more distant parts--also shape mass. A more complex and ambiguous process which employes light and shadow to shape the external form of mass in terms of near adn distant parts, and to create the deep or shallow cavities which comprise its spatial volumes.

These graphic techniques help artists to respond tactilely to the solidity of mass, enabling them to mentally "feel" weight and volume and so impart a greater phenomenological credibility to their drawing... As the eyes follow the visual clues of linear markings tracing the run of surface, together with highlights and shadows which follow suit, we imagine the path of these clues even when they have passed out of sight. [pp. 127-133]