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Material Type: Project; Class: Visual Effects Creature Look Development; Subject: Visual Effects; University: Savannah College of Art and Design; Term: Spring 2004;
Typology: Study Guides, Projects, Research
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8:30 am Introduction Kahrs
8:40 am Lighting from a Filmmaker’s Perspective Poster
10:00 am Break
10:15 pm Storytelling Through Lighting Calahan
12:00 noon Break
1:30 pm A Lighting Approach for Computer Imagery Kahrs
3:00 pm Break
3:15 pm Lighting for Compositing and Integration Carson
Sharon Calahan,Lighting Supervisor Pixar Animation Studios
As the creative Lighting Supervisor for Pixar’s “Toy Story”, Sharon Calahan has been a mem- ber of the technical team at Pixar for the last two years. Her background and education in art and design led her into advertising, broad- cast TV, video production, and eventually com- puter animation. With a focus on lighting direc- tion, Sharon has worked in computer anima- tion for over ten years. Besides “Toy Story” and various commercial work, other accomplish- ments have been as the computer animation Lighting Director for Hanna-Barbera’s “The Last Halloween” which won an Emmy for Spe- cial Effects.
Dave Carson,Visual Effects Supervisor Industrial Light & Magic
Dave Carson has been at ILM for over 15 years, beginning as a storyboard artist and model maker on the second and third Star Wars films. He has worked in various roles on many re- markable films, primarily as a Visual Effects Art Director and Visual Effects Supervisor. His work in the digital realm includes acting as a Digital Artist on “Hook”, “Forrest Gump” and “Jurassic Park”. He also contributed character design and animation on “Casper” where he was credited as Character Design Supervisor. His latest projects include supervising the up- dating of work in “Empire Strikes Back” and “Return of the Jedi” for their new film releases. He is currently scheduled to begin work as a Visual Effects Supervisor on the next film in the Star Wars series when it goes into production later this year.
John Kahrs,Animation Director Blue Sky Productions
John has been directing lighting and animation at Blue Sky Productions since 1990. The focus at Blue Sky has been on a classic approach to character animation, combined with the very best rendering techniques. At the core of the production system is a proprietary raytracer, for which John has written much of the user’s manual. John has made a priority of refining Blue Sky’s lighting techniques. His lighting and animation appears in several commercials for clients including Braun razors, Chock-full-O’- Nuts coffee, and Brother laser printers. John de- signed and constructed the Blue Sky web site. He also has outlined the lighting direction for the CG cockroaches in the upcoming feature film “Joe’s Apartment”. In 1993, John won a Golden Nica Award for his radiosity imagery at the Ars Electronica festival in Linz, Austria.
Steven Poster, A.S.C., Cinematographer
Stephen Poster has worked on dozens of films, including Ridley Scott’s “Someone To Watch Over Me”, “Big Top Pee-Wee” and most re- cently “Roswell,” about the reported crash of a UFO in New Mexico in 1947. Originally from Chicago, Poster was called upon early in his career to shoot second unit photography on “Close Encounters of a Third Kind” and “Blade Runner”.
As I wrote the course notes for my part of the talk, the idea of the course changed drastically. I had thought that the course speakers could teach lighting, plain and simple. I really thought, for some time, that in lighting too, much of the task could be distilled down to an essential list, and my ultimate model for such a list was “The Principles of Animation”, a chap- ter in the indispensable book, The Illusion of Life: Disney Animation , by Frank Thomas and Ollie Johnston.
Then I was on the phone one day with Steven Poster, the cinematographer I asked to speak at the course to offer a look at lighting from a tra- ditional angle. He said out loud what I had been sensing deep down more and more clearly. He said, “Oh, absolutely, no. No, you can’t teach lighting. You can’t teach someone how to light. You can only teach them about light and how it works, and you can give them a few guidelines, but you can’t teach anyone how to light.”
I realized my folly in presuming this. It was like figure drawing class in art school. No one could teach us how to draw. Only we, the stu- dents, could teach ourselves to draw better. The instructor was merely trying to get us to see more clearly: to observe and measure with our eyes and compare what we saw with what we had drawn. If the instructor was good, he was trying to teach us to see.
The process of computer graphics work is like working with a kind of complex diorama-ma- chine. We’re creating little worlds, and we can build everything almost as if from scratch, be-
cause the level of control can be so basic. There are so many different skills to be proficient in when we do this. We have to be Renaissance people.
This course isn’t going to magically transform anyone’s images into flawlessly refined pic- tures. All it can really do is offer a few guide- lines, provide some important things to remem- ber, and hopefully point you in the right direc- tion with a solid footing about where to start.
The artistry of computer lighting has to come from your own vision and intuition about what you want to see. If it succeeds, it may help you see light in a way you hadn’t before, and en- courage you to teach yourself how to create truly great images.
So how to approach the task of lighting on the computer…
John Kahrs New York, May 1996
ABSTRACT
This course is designed as a beginning, non- technical course to discuss the how lighting in computer graphics can be used to enhance vi- sual storytelling for cinematic purposes. It col- lects knowledge and principles from the disci- plines of design, fine art, photography, illustra- tion, cinematography and the psychology of visual perception. Although much of the con- tent of this course is not solely applicable to lighting on the computer, its special needs are always in mind.
The desire to write these notes and to present a course on lighting for storytelling in computer animation arose from the shortage of available literature on the subject. Frequently I am asked to recommend a book or two on lighting, and al- though several good books are available, none are ideal. Most tend to focus on the equipment and mechanics of live-action lighting without explaining how to achieve the fundamental principles. The commonality between live-action lighting and computer lighting is chiefly the thought process, not the equipment. Computer tools vary with implementation, are continually evolving, and are not limited by physics. Tools in the future will be driven by the desire to see on the screen what we are able to visualize in our minds. This course is designed to focus on these thought processes, while providing not only practical information, but also the desire and resources to continue exploring.
The use of words alone is inadequate to de- scribe visual concepts. Most books include many repetitive visual examples to drive the point home. Although a few crude visual ex- amples are included in these notes, they are merely intended to serve as a reminder of the presentation of this course. These notes are also necessarily succinct, and may contain concepts which could not fit into the hour-and-a-half time allotment.
The term lighting in computer animation often includes the task of describing the surface char- acteristics of objects (often referred to as shaders), as well as compositing and the inte- gration of special effects. For the purposes of this course, lighting is defined more in live-ac- tion terms as the design and placement of the lights themselves, but in a purely computer graphics environment.
Visual storytelling is a vast topic that reaches far beyond the realm of lighting. Most of it is not noticeable on a conscious level to the viewer, but adds depth and richness to the story and the visual experience. The lighting principles and techniques presented in this course are dis- cussed in isolation from other visual storytelling devices. Ideally the lighting would be designed with these in mind, but would extend far be- yond the scope of this course.
Cinematic lighting literature typically empha- sizes live-action lighting issues and techniques, and in this discussion of lighting for synthetic cinema we will find that many live-action con- cepts apply. However, there are some differ- ences in the approach, roles and responsibili- ties, the size of the crew, and the sequence in which tasks are accomplished.
By Sharon Calahan
posed image stunning. It can also help rescue a less-than-perfect composition. The principles of composition are the tools with which the light- ing designer can analyze a scene to devise ways to accentuate what is working and to mini- mize what is not. They are effective in both static or moving scenes. Pauses in camera moves and character poses are perfect op- portunities to evaluate a kinetic composi- tion using static techniques.
Rather than simply referring the reader at this point to consult a book on composi- tion, a brief discussion of the primary principles needed to the lighting designer are presented here. Although each prin- ciple relates to the others, they are presented in isolation for clarity.
3.1 Unity/Harmony The name of this principle suggests that the elements of the composition appear to belong together, relate to each other, and to otherwise visually agree. Where other principles of com- position break down the image into spe- cific topics for study, the principle of unity reminds the artist to take a step back and look at the image as a whole.
Although most artists rely on intuition to decide if a composition is working, the cognitive psychologists offer a somewhat less subjective alternative. They study the eye and brain processes that lead to the artist’s intuitive decisions. The cognitive psychologists have developed the Gestalt theory to help explain our perceptual tenden- cies. The term Gestalt means “whole” or “pat- tern.” Gestaltists emphasize the importance of organization and patterning in enabling the viewer to perceive the whole stimulus rather than discerning it only as discrete parts. They propose a set of laws of organization that re- flect how people perceive form. Without these organizational rules, our world would be visu- ally overwhelming. They include:
By ignoring these principles, an artist risks cre- ating an image which challenges the eye to or- ganize it with little success. The viewer’s eye will quickly tire and lose interest. Conversely, too much unity can be boring; if there is noth- ing to visually resolve, the eye will also quickly lose interest.
By understanding how the eye tends to group objects together, the lighting designer can help unify a disorganized or busy composition with careful shadow placement, or by minimiz- ing or emphasizing certain elements with light and color.
3.2 Emphasis To direct the viewer’s eye, an image needs a point of emphasis, or focal point. An image without emphasis is like wallpaper, the eye has no particular place to look and no reward for having tried. Images which are lit with de- fault or uniform lighting similarly feel drab and lifeless. By establishing the quantity, placement and intensities of focal points, the lighting designer directs the attention of the viewer by giving him something interesting to look at, but without overwhelming the viewer with too much of a good thing.
A composition may have more than one focal point, but one should dominate. The more com- plicated an image is, the more necessary points of emphasis are to help organize the elements. Introducing a focal point is not difficult, but it should be created with some subtlety and a sense of restraint. It must remain a part of the overall design.
By first understanding what attracts the eye, the lighting designer can then devise methods to minimize areas which distract the viewer by commanding unwanted attention, and in- stead create more emphasis in areas which should be getting the viewer’s attention.
3.2.1 Emphasis Through Contrasts The primary method for achieving emphasis is by establishing contrast. Contrast can be achieved with shape, size, color, texture, bright- ness or even motion. A focal point results when one element differs significantly from other ele- ments. This difference interrupts the overall feel- ing or pattern, which automatically attracts the eye. With one dark dot among thirty bright ones, there is no question which dot gets noticed, the dark one, for two reasons: it has the most contrast with its background, but also because it is the only one of its type. Unique or minority elements within larger groups tend to attract our attention.
Contrast in value (brightness) is easy for the eye to see, which is why black and white imagery is successful despite its lack of color. It also illus- trates why lighting is a major tool in the estab- lishment of emphasis and directing the eye of the viewer.
3.2.2 Emphasis Through Tangents Tangents, where two edges just touch each other, can produce a strong point of emphasis
may be helpful in recognizing why an object might be attracting more attention than other- wise expected.
3.2.6 Emphasis Through Recognition Because of the human need for self-recognition, human or anthropomorphic characters will naturally attract more attention than inanimate objects. Furthermore, in our attempt to recog- nize a character, we naturally are attracted to look at his face, and especially to his eyes if he is speaking, to see what he is thinking and feeling.
3.2.7 Emphasis Through Motion A static image has static points of emphasis and all principles of emphasis apply, but a moving image has the added bonus of being able to cre- ate emphasis through motion. Camera motion and character acting are topics unto themselves (see [Lasseter87]), but it helps to understand when the eye is attracted to moving objects and when it is not. If all objects are moving except one, the eye will be drawn to the one which is not moving. The opposite case, of only one ob- ject moving, is more common and even more effective in attracting attention.
3.3 Balance When an object is unbalanced, it looks as though it will topple over. Instinctively the viewer wants to place it upright or straighten it. An un- balanced object is distracting and calls attention to itself. An entire image which is off-balance will make the viewer uncomfortable because he wants to balance it, but cannot. This discomfort can be desirable if it enhances the mood or storypoint. By knowing ways to balance or in- tentionally unbalance an image, the lighting de- signer can affect the mood of the scene.
A scale is balanced by putting equal weight on both sides. It doesn’t matter how large or dense the objects placed on the scale are, they will bal-
ance as long as they have equal weight. The bal- ancing of a composition is similar except that vi- sual interest becomes the unit of measure. Visual interest comes in many shapes, sizes, values, col- ors and textures, each with varying density. The principles of emphasis and balance are therefore related since points of emphasis carry visual weight which must be considered when evaluat- ing the balance of an image.
Visual balance is achieved using two equations. The first balances the image around a horizon- tal axis, where the two halves, top and bottom, should achieve a sense of equilibrium. Al- though it is desirable to have a sense of equal distribution, because of gravity, the viewer is accustomed to this horizontal axis being placed lower than the middle of the frame.
Besides helping to create a pleasing image, the top/bottom weight ratio can also have a storytelling effect. The majority of constant fac- tors in our visual life experience tend to be horizontal in nature—the groundplane beneath our feet, the horizon in the distance, the sur- faces of water. Where these horizontal divisions are, relative to where we are, tells us how tall we are, how far off the ground we might be, or whether we might bump our heads on some- thing. Because we are accustomed to making these comparisons, the placement of a character within the image format and the angle that the camera sees him can imply the height of a char- acter. And since we tend to associate height as a dominating physical characteristic, it can say something about the importance of the charac- ter in his current situation. In one shot a short character is placed high in the frame, in the next shot a tall character is placed lower in the frame. The shorter character in the first shot feels taller and more important to us than the character who is actually taller but is visually subservient. A character’s eyes are usually placed above the center line, unless the charac- ter is looking up.
The second equation of visual balance divides the image around a central vertical axis. The horizontal format of cinema is most affected by this left/right ratio. And with the possibilities of action entering and exiting the frame, or camera pans and dollies, this ratio has the po- tential to be very dynamic.
The simplest type of left/right balance is sym- metrical balance, where the two sides are mir- ror images of each other. Symmetrical balance is discussed here primarily because it is easy to understand and to achieve. Heavily used in architecture, symmetrical balance feels very formal, permanent, strong, calm and stable. In other forms of art, perfect symmetry is rarely seen. One distinct advantage of symmetry is the immediate creation and emphasis of a fo- cal point. With two similar sides, there is an ob- vious visual importance to whatever element is placed on the center axis. Another asset is its ability to easily organize busy, complex ele- ments into a coherent whole. In film, symmetri- cal balance is sometimes used to help portray a formal, official, or religious environment or mood. The Ingmar Bergman film “Winter Light” uses symmetrical balance to impart stiff, claustrophobic formality to the church setting in the opening sequence.
In contrast to symmetrical balance, asymmetrical balance is more commonly used, more natural in feeling, and much more challenging to achieve. Although asymmetry appears more casual and less planned than symmetry, its vi- sual ease belies the difficulty in its creation. Balance must be achieved with dissimilar ele- ments by manipulating the visual interest of each. Some of the variables to manipulate are value, color, shape, texture, position and eye direction. Each are discussed here individually for clarity, but keep in mind that the interplay of these variables will affect the end result. Color can balance value, or texture can bal- ance shape, infinite combinations are possible.
3.3.1 Balance by Value We have already discussed that the eye is at- tracted to contrasts, particularly that a high con- trast area attracts more interest than one of low contrast. To balance the scale, a small area of high contrast will command an equal amount of attention as a large, low contrast area.
When it comes to projecting film in a theatre, the value scale isn’t necessarily level to begin with. A theatre is dark to draw the viewers at- tention to the screen. In general, the eye is at- tracted to bright areas more than it is dark ones, and in a dark theatre, with our pupils di- lated, a bright area will attract even more atten- tion since it contrasts with the darkness of the theatre environment itself.
3.3.2 Balance by Color Like value, color can be a balancing element. The eye is more attracted to a color than to a neutral image, the more saturated the color, the more attention it grabs. A small area of bright
Although it may not always be possible to move an object in the scene to balance the composi- tion, affecting an object’s visual weight can be achieved with lighting, either by changing the visual weight of the object itself, or by counter- balancing it with more visual weight elsewhere.
3.3.6 Balance by Eye Direction Every edge, shape or group implies a direction of some kind, either straight or curved. It is the counter-balancing of one direction with another which stabilizes an image.
Directional lines, such as perspective angles, are a simple example of how eye direction can be used to balance a heavier side by pointing to- ward the lighter side, transferring visual impor- tance. Perspective angles are an example which tend to be fairly subtle. A linear object, a shadow edge or the edge of a light can achieve a stronger directional effect. Eye direction also occurs when the eye is led from one side of an image to the opposite side when it finds the same color, or when the eye follows the gaze of a character.
3.3.7 Balance by Physical Weight The perceived physical weight of objects in the scene also contributes to the sense of visual balance. An object known to the viewer to be heavy in physical weight will impart more visual weight than it would otherwise due to our tendency to factor mass and gravity into the equation.
3.4 Scale and Proportion The term scale refers to overall size, whereas proportion is used to describe relative size. Scale and proportion principles help the viewer orga- nize an image. They can also be used to create or minimize points of emphasis.
Scale and proportion are connected to empha- sis and balance. If an object is out-of-scale or is oddly proportioned, it can create too much em- phasis. Large scale elements, especially those large in proportion to the other elements, also create obvious visual weight. The brain auto- matically reads larger objects to be nearer and more important than smaller objects. As an example, in a close-up shot of a character, the viewer is rarely distracted by the background. But in a wide shot containing many elements, the viewer must create relationships between elements to establish perspective and to find a focal point. In addition to mere size grabbing viewer attention, the brain will notice an ob- ject which appears out of proportion, or un- natural in size, compared with other objects. The lighting designer may need to minimize large objects which should not be the focus of attention.
In a purely computer generated environment, the viewer works harder to establish and main- tain size relationships since there is no direct comparison available to the real world. In “Toy Story”, the architecture, furniture, props and characters were modelled and textured with an appropriate amount of detail for their rela- tive size as well as to the distance they would be viewed from the camera. Great care was also taken in the staging and editing processes to avoid disorienting the viewer with unex- pected changes in apparent size relationships. A consistent use of lenses for close-ups, me- dium shots and long shots helped to ensure spacial continuity.
Besides being useful for describing relative size, proportion also pertains to the pleasing design of objects and their placement in the overall image frame. Placing the focal point dead-center in the frame is not usually a very interesting or pleasing placement. The eye naturally prefers the focal point to be located within one of the four quadrants. This is espe- cially true if the image contains another strong point of emphasis. This is only a general rule of thumb, however. Sometimes the lighting de- signer will be given a shot where the focal point is intended to be in the center of the frame. If the shot is a wide shot with many ele- ments, the eye may have difficulty remaining in the center of the screen. It may be necessary to minimize other points of emphasis on the pe- riphery to keep the eye from wandering.
Much study has been devoted to deriving ideal proportions for an individual entity as well as how to portion an image in the most pleasing form. The use of aesthetic formulas has a long history. Even before the Renaissance, when there was more overlap between the arts and sciences, artists and mathematicians perfected what they believed were the ideal proportions for human form, design and composition. One of the formulas they derived is the golden sec- tion*. Once used heavily in architecture, paint- ing and sculpture, it is described as “Tradi- tional proportion which is supposed to express the secret of visual harmony. In its simplest form it consists of a line divided into two so that the smaller part is to the larger as the larger is to the whole.” This proportion is ex- pressed in mathematics as a Fibonacci sequence of numbers, or as a ratio roughly equivalent to 8:13 (j). The golden section is frequently found in nature and is very pleasing to the eye. When deciding where to place an edge of a light or
shadow, formulas like the golden section may be useful to keep in mind.
3.5 Repetition and Rhythm 3.5.1 Repetition of Shape The use of similarly shaped elements in an im- age, however subtle, is a strongly unifying force, as a product of the Gestalt grouping prin- ciple. Repetition is an aspect of visual unity which is exhibited in some manner in every im- age. The human eye is very good at making comparisons and correcting minor differences to equate two shapes as being essentially the same, and then grouping them together as a unit or connecting them in some way. Because of this tendency, two similar objects, even at opposite sides of the image, will lead the eye from one shape to the other.
Also, the shape of an object can acquire more visual weight if it is repeated, by its own shadow for instance. By looking for ways to re- peat shapes with light and shadow, the lighting designer can help unify an image or redistrib- ute visual weight
3.5.2 Rhythm Visual rhythms are plentiful in nature: a stand of trees, a flock of birds, ripples in the sand, raindrops in a puddle. A person is so accus- tomed to natural rhythm that they feel it more than they see it.
As a design principle, rhythm is based on rep- etition, although just because something re- peats itself doesn’t mean it has rhythm. A small number of repeated or similar elements become visually grouped together to form a unit. To achieve rhythm, a larger number of elements are required, enough elements so as to discour- age grouping as a single unit, but several. Groupings of three or more start to introduce rhythm, but only if they are not exactly the same. Rhythm also requires variation within its repetitive groupings.
*p. 90; * The Thames and Hudson Dictionary of Art Terms , by Edward Lucie-Smith: Thames and Hudson, 1984.
