Photon Paint: The Art of Lighting

"...the object of art is not to reproduce reality, but to create a reality of the same intensity." - Alberto Giacometti

The fundamental intent of the lighting process is to create a synthetic visual reality that captures the emotion and atmosphere of the story. Augmenting reality to create imagery that appears real to your audience requires a shift in your perception of light and lighting in the world around you. Simply reproducing what you see isn't enough.

Vincent Van Gogh said, "I often think that the night is more alive and more richly colored than the day." To Van Gogh, the night sky was not simply black; it was full of brilliant and deep blues and purples, patterned with glowing yellow stars. His perception of the color and play of light in the night sky wasn't based on an uneducated guess; it was an insight earned through dedicated observation and artistic experimentation.

Your path to learning the language of light starts in your own observation of nature and ends when you can create a reality of the same intensity. Your task as a digital artist is to create images that are more real than real.

This chapter introduces you to one of the most amazing and creative parts of digital content creation: how light affects the appearance of the materials used in your models and how to use lighting to create depth, mood, and atmosphere in your visual imagery.

Introduction to Lighting Theory, Principles, and Practice

"The finest thing we can experience is the mysterious. It is the fundamental emotion, which stands at the cradle of true art and true science. He who does not know it and can no longer wonder, no longer feel amazement, is as good as dead, a snuffed-out candle." - Albert Einstein

Einstein's powerful words establish a common origin for both science and art—the exploration of the mysterious. The goal of lighting design is to help create amazement and wonder in the audience. The audience wants to experience the mysterious, and lighting is a powerful tool to help you accomplish that task.

This Workshop contains only a small portion of all there is to know about lighting. However, there are some fundamental theories, principles, and processes that must be presented to establish your foundation of basic lighting principles, theory, and technique.

During your career as a max artist, you will be asked to create the lighting for many diverse scenes. Knowing how to light a room at twilight, a desert under a full moon, or a rainy night on the docks in San Francisco is based on an understanding of why light behaves as it does and the principles governing the artistic use of lighting in your scenes.

Radiosity: Creating the Illusion of Reality

"In order to paint absolute truth, you must lie a little." - Monet

Raytracing is a rendering algorithm that partially simulates real-world lighting by tracing the paths of incident rays of light from a light source through 3D space. Although raytracing results in a realistic reflected and refracted light phenomenon, it doesn't create the complete complexity of real-world lighting known as radiosity.

Radiosity plug-ins are available for 3ds max 4 that can create radiosity lighting and rendering for your scenes; however, they come with a cost, both in terms of money to purchase the software and the magnitude of time it will take your system to render each frame of a shot. Radiosity rendering algorithms are good at reproducing reality, but they cannot replace the experienced eye of an excellent artist. When you understand the basic principles behind radiosity, you'll understand that the lighting effect can easily be created using the basic lighting tools and material options available in 3ds max 4. You can fake it! Or as Monet says, you can "lie a little." The first step in learning to fake radiosity is to understand some of the science at the core of lighting and color perception.

Light Bounces

"Science is spectral analysis. Art is light synthesis." - Karl Kraus

Both spheres shown in Figure 5.1 are mapped with a shiny nonreflective material and have strong highlights that help define their spherical form. The difference between the two is seen in how the light reflects onto the side of the sphere away from the key light source. No fill light can be seen in the back-bottom edges of the sphere on the left. This creates a visual problem—the bottom and side edges of the sphere are undefined and are visually lost in the checkerboard of the ground plane.

The back and bottom edges of the sphere on the right, however, are reflecting bounced light—simulating the ambient light effect of radiosity. Synthesizing radiosity can be accomplished by adding additional fill lights to your scene or by adjusting specialized parameters in your object materials. In the case of the sphere on the right in Figure 5.1, an extra light in the scene did not light its edges. The ambient light radiosity effect was achieved by adjusting the parameters of the material applied to the sphere.

Light Energy and Color Perception

"Yes, I answered her last night; No, this morning, sir I say, Colours seen by candlelight, will not look the same by day." - Elizabeth Barrett Browning

One of the most important factors to understand about creating your scene lighting is the relationship between light energy and color. Lower light energy results in a corresponding reduction in reflected light and a subsequent reduction in your eye's physical ability to see color and value.

Filmmakers and lighting designers have grappled with the chronic challenge of how to effectively create night scenes and other low-level lighting conditions. The solutions have been varied, somewhat crude and often ingenious. In the 1950s, filmmakers

would just use a dark filter on their camera lenses and shoot their night shots in broad daylight. This was the reality of the technical limitations of film, film processing, and available technical lighting at the time. Although the audience accepted the imagery then, it is doubtful that such a solution would be viable today.

The triumph of the digital artist is the ability to use imaginary color and lighting to simulate the effect of night without losing important image elements to the shadows. Understanding exactly what's happening under different lighting conditions and why "...colours seen by candlelight, will not look the same by day" is critical to your mastery of digital lighting.

The visible spectrum of light is a small part of the vast electromagnetic energy surrounding you. Light that cannot be seen, such as X-rays, radio waves, ultraviolet light, and infrared light, lies outside the boundaries of the visible spectrum.

Your eye processes light information by using specialized cells called rods and cones found in the retina. The retinal membrane in your eye is approximately the size of a postage stamp and contains 100 million rods and 3 million cones. The rod cells are sensitive to differences between light and dark and help you see and interpret object shape and movement. Cones are the color-sensing cells in the retina and require more light energy to be activated.

During the middle of the day, the sun's direct light is at its most powerful—illuminating everything in its path. Under such powerful illumination, all the colors in the visible spectrum can be seen. On an overcast day, when light energy is reduced through atmospheric conditions, object colors appear less vibrant or even colorless. During twilight, colors at the red end of the spectrum become gray, blending in with the shadows in the environment, and becoming almost impossible to see.

After a long history of twilight accidents, many emergency vehicles are now painted in optic yellow or optic green instead of traditional red. Optic green and yellow appear white under low and indirect lighting conditions, making them easier to see at night. This is also one of the reasons fluorescent green and orange tennis balls were created—they are easier to see during twilight, a favorite time of day for recreational tennis.

The excerpt from the poem "Late Lament" by Graeme Edge of the Moody Blues given at the end of Chapter 4, "Visual Touch: The Art of Material and Texture Development," illustrates the basic relationship between color perception and light. The "Cold-hearted orb that rules the night" is the moon, which reflects about 10% of the sunlight striking it. The moon provides enough light to allow your eyes to recognize shapes and perceive motion. However, there isn't enough light to activate the cone cells in the eyes, thus removing "the colors from our sight." Under such low-level lighting, the color red is seen as gray and yellow appears white. Other colors exhibit similar perceptual changes under low lighting and indirect light levels.

Creating the Emotional Context of Lighting

"A work of art which did not begin in emotion is not art." - Paul Cézanne

To understand light and lighting, you must study the scientific basis of its creation. But your task as an artist is to bend, break, or make up new rules as you go to achieve the atmosphere and emotion of the story—to "create a reality of the same intensity," as Giacometti said.

The movies The Matrix and Saving Private Ryan are great examples of how light and color are used to create a visual reality that taps into the emotions of the audience. They are also great examples of the intentional use of lighting to capture and convey emotional content. Consider the opening scene of Saving Private Ryan and the lighting design of The Matrix.

Saving Private Ryan

Director Steven Spielberg and cinematographer Janusz Kaminski wanted to capture the terror, slaughter, and chaos of the invasion at Omaha Beach, D-Day, June 6, 1944. To accomplish this technically, they used handheld cameras with lenses that had been modified by stripping out the black coating on the interior of the lens bodies. The interior surfaces of modern cinematography lenses are coated with a nonreflective matte finish to eliminate internal light reflection.

Modifying the lens in this way created a higher contrast image reminiscent of the black-and-white newsreels seen during World War II. The overcast indirect natural light of the French oceanside, coupled with the high-contrast images produced by the lenses, enhanced the viewer's perception of motion in the scene. This is a masterpiece of value contrast and the use of lighting to capture story and emotion.

The Matrix

Bill Pope was the director of photography on The Matrix and had this to say about the lighting, color, and emotion they were trying to create.

"To distinguish the Matrix from 'reality,' from the Nebuchadnezzar and the pods, 'reality' was given a cooler look, a bluer, more normal, less sickly look. The future in the film is cold, the sun is blotted out, there is no real warmth unless it is artificial heat, so that is why they went for the cool side.

"Whereas the Matrix, created by the computers, is a decadent, decaying world, so it has a green hue. These are the two different colors—green and blue. The Matrix should make you feel sick, and in 'reality' you should feel a little more at home, but never comfortable. If you make it gold and warm you know that it is home, a safe haven. The other day I started using warm lights—I did this unconsciously for the first time in Neo's bedroom. It just felt right that it should be slightly warm. As harsh as that bunk is, it is the only home he has got." (from an interview published on the official The Matrix Web site).

This reveals the consideration given to creating the differences between the reality Neo finds himself thrust into and the unreal world of the Matrix. The use of some warm light in Neo's apartment to create the feeling of home is a subtle and powerful example of how lighting is employed to reinforce the feelings naturally occurring in the hearts of the audience: Home should be warm, comfy, and safe.

Painting with Light

"...instead of trying to reproduce exactly what I see before my eyes, I use color more arbitrarily so as to express myself forcibly." - Vincent Van Gogh

A single Workshop like this can't contain an exhaustive treatise on color theory and how to paint with light. But a simplified explanation of the basic approach taken when lighting a scene will set the foundation for your own experiments. For greater detail on lighting, read Jeremy Birn's Digital Lighting and Rendering. The following sections detail the basic concepts to keep in mind when lighting a scene.

Light Color and Material Color Interaction

The color of the light in your scenes changes the color of the material it is illuminating. For example, a red light turns a light-colored material red and turns a bright green material black. Multiple lights in a scene also add their color to each other. For example, overlapping red, green, and blue spotlights creates white light at the nexus of their intersection.

Plan for this in advance by choosing material colors that work with the lighting color design of the scene.

Lighting and Painting Analog

"My choice of colours does not rest on any scientific theory; it is based on observation, on feeling, on the very nature of each experience." - Henri Matisse

In traditional painting techniques, opaque paint is used to model the forms of the objects seen in the image. The term model in this context means to render the contours of the form using only light and dark tones. After the light and dark values are completed, transparent color glazes are applied to create the color seen in the image. The process continues in a cycle of building up opaque value layers and glazing for color until the painting is complete.

The analog to this technique in digital content creation is to use the diffuse and ambient color components of the materials to model the light and dark values of your objects. Then use lights to create glazes of color for your objects. This is the main principle behind using color in lighting.

Sometimes the diffuse color of the material needs to be less intense and more neutral (less colorful or saturated) to allow the color of the light to create the color seen on the object. You won't see the need for this kind of adjustment to your object material until you are lighting your shot. Using layers to create your scenes enables you to easily accommodate this kind of change to achieve the lighting effect you desire.