11

SHADING AND RENDERING

What we interpret as lines in optical reality are actually the contrasts between and among surfaces and tonal differences, as illustrated to the right.

The choice of how one shades or renders these surfaces is ultimately a matter of fitness to purpose, style, and creativity.

The methods and styles for shading in surfaces can range from the lightest gestural suggestions to all the details and gradations of photorealistic rendering, and with everything in between.

SKETCHING SURFACE TONES

Line Quality

It is possible to suggest tonal differences and three-dimensional form by manipulating the weight of line alone. By making some lines darker and others lighter, highlights and shadows can be implied.

Line Shading and Hatching

Surfaces tones can be indicated by dots, lines, hatching patterns, or virtually any kind of disturbance that sets off one area against another. In sketching, sometimes a simple squiggled line will not only be adequate but also most effective.

SHADING WITH PARALLEL LINES

Using parallel lines is one way to get a surface. But notice the optical effects when shadow lines are parallel to the lines describing the form, as in A and B. Here, it is easy to confuse the shading with a corrugated texture on the surface. The diagonal lines in C are less likely to be confused with the form's texture and more readily perceived as a tone on the surface.

Parallel lines on curved surfaces act quite differently. Note that in cylinder D, where the lines run on the straight axis, the roundness of the cylinder is reinforced. In E and F, where the lines run against the curve, the shadow tends to flatten out the curved surface. In H and I, the parallel lines follow the curve and again reinforce it.

By combining these sets of lines, a wide range of hatched tones can be developed. How these are handled is ultimately a matter of style and aesthetic judgment.

RENDERING CONTINUOUS TONES

There are many ways to fill in a surface. Pens, pencils, markers, brushes, and computer commands all demand their own procedures. Here is a general suggestion for shading in a continuous tone with pencils and similar sharp tools.

1. Start with diagonal strokes at a corner, then pull back into the surface.

2. Slightly change the angle of the stroke and re-cover the same area.

3. Shift the angle again until all evidence of the undersurface is gone.

4. Once the primary surface is done, shade from sides back to middle.

5. Finally, work down the overall tone until the outline lines disappear.

If carried to an extreme, the technique itself can become transparent–photorealistic. As exciting and admirable as this might be from a technical point of view, it is not always practical or aesthetically desirable.

1. Sketch in the object lightly after working out its perspective and shadows. If the outline is too dark, you will have to overdarken the shadows to make the lines disappear.

2. Lay in the main shadows lightly. It is a good idea to use different line directions for each surface.

3. By changing angles, work the tones down to the desired levels.

4. After you have the various tones where you want them, finish off with final details and clean up the remaining guidelines and outlines.

Shading Rigid Surfaces

SHADING FLEXIBLE SURFACES

Cloth, paper, and other flexible materials pose special problems in rendering due to the complexity of possible forms. Nevertheless, there is order underlying these seemingly endless variations.

• The character of folds reflects the nature of the material.
• Most folds result from material being crushed or pulled.
• Most folds reveal some internal or external point of support.

Thin, rigid materials like paper, foil, or sheet metal create sharp folds and angular facets.

The high contrast (left) provides a powerful impression but gives little detail, while the continuous gradations of tones (right) allow for more subtlety.

To help maintain consistency in complex shading problems (center), it is a good idea to start by dividing the range of shadows into four or five discrete tones, then proceed to fill in the in-between tones.

The style and technique of shading are important factors in communication. This drawing for a preservation campaign was intentionally finished with hatch lines to mimic a nineteenth-century engraving, to be in keeping with the subject's historic character.