Virtual Cinematography
The Basics of lighing a 3D set.
by Andrew Weiler

More than any other aspect of 3D design and animation, what can really make or break a scene is the lighting. It's not surprising that many proffesional CG lighting directors (often referred to as the "TD" for Technical Director) come from traditional film and fine arts backgrounds, the ability to apply real-world solutions and effects to the digital stage is the key effective lighting.

CG lighting involves a lot of "cheats", because software is unable to calculate the multitude of subtle shading, coloration, and reflection effects produced in the real world. My office, for example, is lit by one window and a torchier lamp. The majority of the lighting I use for reading and working is not directly from these sources, but diffused light boucing off the walls and ceiling. If my office were reproduced in 3D software I would be unable to light it realistically using only two light sources, because the renderer would only reproduce the direct illumination. For example, to reproduce the effect of bounce-light coming off my blue carpet onto the white walls I would need to place a a blue-colored light under the floor facing up toward the walls with a sharp falloff value. The same method would be used to simulate the light bouncing off the ceiling from the torchier lamp. Don't feel constrained by what's "real", remember that if it looks right it is right.

Another key is pre-planning. If you know the mood and feel you're trying to achieve things will proceed much more smoothly than throwing a few lights into the scene and trying to tweak it till it looks good. A good foundation to start from is using the three-point lighting method: key light, separation, and fill. The key light is your main light source, usually set off to one side. Separation light is important in that it provides highlights along the edges of your subject to "separate" it from the background. Fill light is usually a softer, more diffused light than the key, use it to soften the shadows and fill in areas opposite the key.

Try to get an even distribution of light, but allow for some breakup to give depth and scale. Also make sure your lights are not all the same color. In daylight scenes the key light is usually yellow, bounce light more toward orange, and fill is blueish. Many 3D sofware packages allow for an "ambient" intensity, this has to do with the level of light independent of any light souce. Although useful for quick render tests, ambient intensity should be set very low or to 0 in most cases; having no origination point it will tend to make things look brittle and plastic.

Figure 1 is an image taken from a recent project I completed, figure 2 shows an overhead view of how the lighting was arranged. Notice the point lights arrayed around the subject, these are non shadow-casting lights that only serve to provide specular highlights to the subject. The fill light is also non-shadow casting. The area light placed above the subject serves to provide separation, as well as soft shadowing.

In conclusion my advice to improving your lighting skills is to keep experimenting, and keep your eyes open for day-to-day observation. Like Monet's various paintings of the Rouen Catherdral, the treatment of light and shadow has everything to do with the expression or emotion you're trying to portray, so make sure your lighting serves your subject.

Andrew Weiler is a CG artist and technical director working in the Atlanta, Georgia area. When not producing animation, graphics and effects for companies like Bellsouth, AT&T, and GE you'll probably find him juggling his kids around, and trying to get some sleep.
http://www.mindspring.com/~aweiler/