Page 336 - Green - Maritime Archaeology: A Technical Handbook. 2nd ed

Chapter 11: Artifact Drawing
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b
Figure 11.13 (Continued)
culminating in the darkest area at the outer periphery (from about 6–10 o’clock). It is best to start shading from the darkest area outward to the lightest. The general rule for shading is to examine the curvatures. There are generally two curvatures, one curvature rotates about a vertical axis, the other rotates around a horizontal axis, and the shading should relate to these curvatures. For example, for a cylindrical object with a semicircular, cross section of beading running around the cylinder, the beading should be shaded first in the horizontal plane (i.e., dark at the left getting lighter toward the right), and then shaded in the vertical plane (light at the top of the beading to dark at the bottom, see Figure 11.14a). As one gets more proficient at shading, it is worth considering using another shading con- vention. Consider two possible lighting situations: one where the light comes from the top right, but in the plane of the object; the second, where the light comes from top right, but out from the plane of the paper (or the object), between the object and the viewer. In the former convention for a sphere the brightest point would be top right, at the periphery, whereas in the latter, it would be top right, but in the center of the top right quadrant (Figure 11.14b and c). Note the Figures 11.14b and c were drawn using a computer graphics package, the latter convention produces a more realistic three-dimensional effect.