RENDERING (SHADING) INREPRESENTATIONALDRAWING

computer graphics & design

What is Rendering?

Rendering is the application of tone and texture to create a three-dimensional

appearance and/or to depict the surface details of an object.

Rendering is important when the communication of the form of an object is required in a design. For instance, if a furniture designer needed to illustrate a new line of chairs, it would be important to depict the characteristics of the fabrics and materials to be used in their production. The rendering of materials, using a range of media, can communicate a great deal of visual information about products and objects.

You may have seen illustrations of proposed designs labelled as an ‘artist’s impression’. For example, architects and interior designers often use these ‘impressions’ to help clients visualise what may otherwise seem to be a complex plan . The use of colour, line and tone to demonstrate surfaces, texture and detail helps to communicate the design ideas.

Rendering Techniques

Effective rendering in design concept development can be achieved through the application of an almost limitless range of media.

Markers pens, ink pens, computer rendering, gouache and pencil are probably the most popular methods, with computer-generated images becoming increasingly common. It is also possible to achieve striking results with combinations of media, as well as pastel, collage, watercolour, cut paper and airbrush.

When rendering images, establish the purpose of your design image before you begin, as this will determine the most suitable medium. Ask yourself, what is the purpose of the drawing?

• Is it to express the realistic form of an object?

• Is it to emphasise a feature or detail?• Is it to create visual interest?• Is it a combination of the above?

Pencil Rendering

Pencils generally consist of a graphite core within a wooden casing. It is also possible to use graphite sticks, which are often thicker and are encased in paper or plastic.

Pencils are available in a variety of grades that affect their rendering qualities. Pencils in B grades are softer and offer a smoother application over larger areas. H grades are hard and are more useful in line work and drafting.

Soft pencils enable you to render a surface with a range of tones by layering applications of tone. When using soft coloured pencils, it is possible to layer similar hues of one colour to generate an intense area of solid colour that can add visual interest. When working with pencils, applying colour thickly may damage the paper surface. Layering is more effective and allows for flexibility.

Use multiple hues of one colour and layer your application of the colour when working with coloured pencils.

Ink Rendering

Rendering with ink requires quite a different approach to working with pencil. Variations in line quality - rather than layers of tone or varying pressure - make the difference in ink-based renderings. You can use fineliners, ink and nibs or technical pens to create detailed renderings or quick sketches. A range of techniques can be used with permanent media such as ink.

Dot Rendering

Dot rendering can be used as an effective method of conveying tonal variation. Dots of a consistent size, but varying in their proximity to one another, create a range of tones that can communicate shadow and highlight areas.

The key is to ensure that you don’t get sloppy with your application of dots. Consistency, though time-consuming, leads to the best results withthis technique. Note that you do not have to fill anentire space to suggest texture and form .

Crosshatching Or Line Rendering

Commonly an ink-pen technique, crosshatching is a rapid method of applying tone that can be very helpful in idea development and in communicating tonal information quickly. Vertical, horizontal and diagonal lines vary in proximity to one another, creating tonal and textural variations. This technique is often used to suggest textures such as fabric, wicker and natural fibrous materials. To ensure the success of this technique, try to keep your line widths consistent.

Marker Rendering

Popular due to its rapid application, marker rendering is commonly used by industrial and product designers to present con cepts. Markers contain intense pigments in an alcohol base, whi ch provide quickdrying colour and are best used on a smooth, nonabsorbent or non-bleeding surface such as bleedproof paper. Markers often have two tips - a broad tip and a fine tip at opposite ends of the pen - allowing for both fine work and the application of larger areas of colour and tone.

The key to effective dot rendering is to keep the dots even and consistent.

Crosshatching is useful in rendering to suggest form; it does not have to be appliedacross an entire object to be effective.

Available in a range of colours, markers are also sold in sets of greys - warm, cool and neutral - which provide scope for rendering products in tonal detail.

Applying markers takes practice and it is advisable to test on rough drafts before applying to a finished pencil or pen drawing.

To create block areas of colour, overlap consistent marker strokes; this will help to disguise streakiness and provide even tone. If using different markers to build tone, use the lightest marker first and build up colour with darker hues as required.

Rendering to Represent Form

In depicting the characteristics of form, the principles remain the same no matter which media you choose to work with .

Light Source

Natural or artificial light influences the appearance of objects, creating highlights and shadow areas. When light from the source hits an object it will often create a highlight, mid tones, dark tones and cast shadows.

Depending on the surface texture of the object, it may also reflect light. It is through the representation of light and dark areas that a three-dimensional form can be depicted. It is, therefore, important to identify the light source as the first step. In daylight, it is sometimes difficult to ascertain the primary source of light but invariably it will be a window or, if outside, the sun. In a dark space, a light globe or lamp will create a light source that will appear more clearly defined than the more diffused light of day, and will create sharp contrasts.

In rendering the form of objects, you may need to make an arbitrary decision about the primary light source, taking into account reflected light from other surfaces or secondary sources of light.

Use even overlapping strokes in a constant motion to develop tones using markers.

Tonal Scale

A good method to use when rendering, regardless of the medium or rendering method, is to first create a tonal scale. A scale becomes a good reference point when rendering, as you can select the tone that best suits your drawing task and chosen medium.

Don’t be afraid of the dark!

When applying tone, use the full tonal scale and don’t be afraid of using truly dark tones. it can be tempting to stick to mid tones that can produce a mediocre grey image. For effective results, resist the mid-tone temptation.

Use a soft pencil such as a 2B or softer to generate areas of shadow. Use the contrast between highlights and dark shadows to emphasise the form of an object.

For example, when the darkest tone is placed next to the lightest tone, the differences between the two are intensified, creating a distinctive and sometimes dramatic lighting effect.

Reference material from Visual Communication VCE Units 1 to 4 by Kristen Guthrie and published by Cengage Learning

The dark tones in this drawing from observation of Mies Van der Rohe’s ‘Barcelona’ chair create strong contrasts that emphasise the form and texture of leather