Rendering - Lighting Issues01

Lighting a scene is often one of those elements of a visual production that goes unnoticed or is taken for granted - until it's done poorly.

Whether the presentation is theatre, TV, film, computer animation, drawing, painting, or design visualization, adding visual depth using light and shadow produces a powerful effect. Not only may the image literally represent another reality but the image maker can orchestrate the scene to specifically direct our attention. The observer has an easier time understanding an image created with the use of light than one rendered flat or purely graphic in nature. Many people in the design or entertainment industry are visually literate enough to see important value in the 'napkin sketch' that offers ideas drawn without shading, color or value. Designers, however, need to show an understanding of how light works to cater to the largest possible audience for their ideas.

The science of lighting is an integral part of the design of a visual in cinematography but curiously absent from the curriculum of industrial design.

Design concepts may be rendered with one light source but most effectively use three: key, fill, and kicker or rim lights. In Figures 01, 02, 03, and 04 from Pixel Cinematography - A Lighting Approach for Computer Graphics by John Kahrs, the author first shows the overall effect of 'standard' studio lighting and then visually separates each.




Fig.01 - Kahrs, J. (1996), p.45 - Studio lighting with key, fill, and kicker lights

   


Fig.02 - Kahrs, J. (1996), p.47 - Key light

  

 

Fig.03 - Kahrs, J. (1996), p.48 - Fill light



 

Fig.04 - Kahrs, J. (1996), p.49 - Kicker or Rim light







In industrial design, a product is generally illuminated from the side with a primary light source, sometimes referred to as an "infinite" light source, similar to the sun: the rays are parallel when casting shadows. The position angle of the light source should be carefully chosen. Too high and there's not enough cast shadow; too low and the cast shadow (dark, contrast) dominates the scene. To show a maximum level of detail and form, scene lighting works best if there is good contrast between the object and the background. To generate many concepts quickly, it often works best to have the background and ground plane as white and the product dark or with color so that the viewer's eye is drawn immediately to the main image. In Figure 05, the contrast of the object makes it the main focal point with a light background. The cast shadow establishes the ground plane. Fill light is seen in the lighter areas of sides 2, 3 representing reflected light from the key light striking the ground. Secondary lighting, shown as the reflected lighter area on the back top surface of the cube, represents the "kicker" lighting.

  
 

Fig.05 - Industrial design concept visualization with light

Often in different types of imagery,

the artist will add color to the lights/

light sources. Comic illustrators may

use a combination of warm and cool

colors in lighting from two sides

(primary/secondary or key/kicker).

Using colors in this way will increase

the visual effect of depth and realism

to the image (see Figure 06.)

 





Fig.06 - Kerlow, I. (2004), p.202

Last week I began to explore some of these lighting issues in Maya with the geometric objects set on a plane.

With only marginal knowledge of the lighting systems available in the software, I set a primary light as shown previously and then an Ambient light thinking it might work as a fill/kicker light source. Working with the two variables of light Intensity and Ambient Shade I was able to insert secondary fill/reflected lighting with different colors, one cool and one war(Figure07,08.)

Fig.07 - Blue reflected ambient light

 






Fig.08 - Ochre/ground tone reflected ambient light

It wasn't until Zach Maynard, one of the resident experts in computer visualization at ACCAD, happened to give me a primer on the different lighting options available that could best accomplish what I was trying to visualize. He set up the same scene with a new camera angle, the key light and a bounce/fill light that would show reflected light in the dark areas of the shading and cast shadows (Figure 09.)



 



 

Fig.09 - Zach M. layout with reflected fill light

 

The most important discovery of this process for me was a closer understanding of the differences in approach to lighting the two endeavors use. Industrial designers usually consider one light source and a simplified cast shadow color of black. Knowledge of lighting science is not critical since design drawings may be successful in a graphic instead of realistic nature. Industrial designers using 3D modeling programs generally do not have the background in cinematographic lighting conventions briefly explained above and learn 'on the job'. Computer modelers and animators, however, are required by the medium to learn these skills to keep pace with the audiences demand for realism. The differences between key, fill, kicker, ambient, spot, point, area, and infinite lights are specific and purpose-driven. The nature of light illuminating a surface is a powerful tool in describing form for any design medium.

The other discovery is how one must analyze the effects sought in a computer rendering setting before choosing the light specific to that requirement. For example, a bounce or fill light is best obtained steering a direct/key light through the underside of a plane to the underside of the object and adjusting the surface character variables (diffuse/reflective, specularity, transluscency, color, etc.) to effect the desired aesthetic. This procedure will be discussed further in the next post.
 
References

Calahan, Sharon (1996), Storytelling Through Lighting - A Computer Graphics Perspective. Siggraph '96 Course #30.

Kahrs, John (1996), Pixel Cinematography - Lighting for Computer Graphics. Siggraph '96 Course #30.

Kerlow, Isaac V. (2004), The Art of 3D Computer Animation and Effects. Hoboken, NJ: John Wiley & Sons.