Line Weight Line Color and Shading In almost all technical illustrations, lines are drawn in black. Occasionally, if the illustration incorporates shading, another convention may apply in which some interior lines are drawn in white, like a highlight. This technique may be the representation of the real white highlights as can be seen on edges of the mechanical part in Figure 8 . By using this convention, lines drawn in black and white suggest a light source, and denote the model's orientation.
Illustrators sometimes use the convention of white interior edge lines to produce a highlight.
An image produced by our system, including shading, silhouettes, and white crease lines.