Lighting Tips - Featuring Coney!

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Part 1 - Introduction

This Guide is meant to be a starting point for lighting in the CG world. These tips and techniques will be skewed towards a gaming environment with an emphasis on storytelling. There will be information here that has been covered many times before, but hopefully there will be something that sheds some light on how to apply traditional film and illustration techniques to the world of computer graphics.

For our purpose we will be employing a lighting style called "Practical Lighting" This is a technique that uses visible or actual light sources to create the lighting scheme. In film a practical light is any light that is visible on the screen. Because of the third dimension and the ability to explore in game environments, In our case any light source could be a considered a practical light. Lamps, torches, candles, ghosts and of course boiling pots of human flesh can all be practical lights.

I would guess 80% of our lights will be practical lights. This will create a believable environment that comes to life for the player. To augment these practical lights and to have further control over the look of the environment and the player's experience we will also have "Local Spotlights." These lights will make up the last 20% of our lights. Local spots are used to control the brightness of a specific area. This will give explicit control over the visibility of areas, objects and puzzles while still retaining the overall feeling and contrast of an environment. Local lights can also be uses to control the ambient light of a scene.

With the addition of "Radiosity" or Global Illumination we have an opportunity to bring even more subtle, believable and even spectacular lighting to our environments. While there is still some work to be done in figuring out how to incorporate this new feature into our lighting work flow, I am confident and excited in the prospects that it offers. Keep in mind, however, radiosity is still no substitute for a good understanding of lighting and composition.

Part 2 - 3-Point-Setup

Let's talk about traditional lighting set ups. The most popular, if not most common, of light set ups is the 3-point lighting scheme. This setup allows the subject to be modeled by the light. The three lights bring out the subjects dimensionality.

The three types of light are called Key, Fill and Back lights. Each of the three points has a specific function.

Key Light: This is the main light source in the scene. It is also typically the brightest. Lamps, chandeliers, torches and even the sun would be depicted with the key light. Key lights are most often practical lights. If it is not a practical light placement of the key is often 30-45 degrees of the cameras axis and slightly higher than the subject. We will talk about color in the Quality and Color section.

In this movie you can see Coney lit by a very generic 3-point light set up.

Fill Light: This type of light can be a secondary light source or reflected light. It is commonly the dimmest of the three lights. Fill lights are commonly placed on the opposite side of the cameras axis as the Key light. The color can be complimentary to the color of the key. For example, if the key is warm then the fill would be cool.

Back Light: This final of the three lights is used to create edges on the subject. Back lights are most often used to enhance the shape of the subject and separate it from the back ground. Most often it is located directly opposite of the camera and is placed above the subject. Because they are often used to create silhouettes or edges of the subject they are also referred to as rim lights, hair lights, or even kickers. In some cases more than one Back light is used to help define the edge of the subject and make it pop from the background.

By placing the Key Light in different positions relative to the subject various moods can be achieved. This will be discussed in more depth in the Time of Day and Mood section. For now let's just look at a couple of common lighting schemes.

Low Angle: A Light that come from below the subject is often referred to as a "Light From Hell." Evil characters are lit this way and it instantly reminds us of flashlights and campfires.

High Angle: A light that comes from directly above the subject can be really creepy. Whenever eyes are in shadow it gives a strange feeling. A dim fill light can partially reveal the eyes are dark shadow areas.

In this movie three different lighting schemes can be seen. Camera angles used in conjunction with lighting angles go far in creating a specific look for a scene.

Back Lit: A Light that come in from behind the subject is called, you guessed it, a back light. So the Back light takes the place of the key light as the dominate source of light in a scene. This is great for creating a silhouette of a character and creates a mysterious feeling.

Part 3 - Key-to-Fill Ratio

Key- to-Fill ratio is a simple equation that describes the relationship between the Key light and the Fill light. A key light that is twice the brightness of its fill light has a Key-to-Fill ratio of 2:1. This ratio would be considered a Low Key-to-Fill ratio. A scene with a ratio of 18:1 would have a High Key-to-fill ratio.

Low Key-to-Fill ratios are most often used to depict a snow or overcast day or bright interiors. Shadows would be washed out by the reflected light. Typically Low Key-to-Fill ratios create more of a happy lighting scheme. When you are buying your Super Slushy in the Quicky-Mart you are in a Low key-to-fill ratio environment. We will be discussing ways in the Time of Day and Mood section on how to create more gloomy lighting using lower ratios.

High Key-too Fill ratios can be used for bright daytime light with dark shadows, night scenes or to build suspense and drama through severe lighting. This technique of using high ratios is best seen in Film Noir.

The well executed use of these techniques can go greatly to enhance mood and suspense throughout a scene or sequence. Remember that continuity from scene to scene is important, as well as the use of temporal contrast to enhance a change of location or even the story conflict.

Part 4 - Quality of Light and Colour Balance

In this example you can see the difference between Hard light and Soft light

Without getting to deep into color theory I would like to discuss Quality of Light and Color Balance.

There are only two real Qualities of Light, Soft and Hard. Thus creating two types of shadows, soft and hard. We can also call it sunny or cloudy. The hardest light would be generated by the sun on a very clear day, and the softest light would be created by the sun on a very overcast day. It is the millions of particles floating in the air that bounce and catch the light. These particles then refract, reflect and scatter the light from the sun creating all the wonderful variants of light we see everyday. The more the light bounces around and gets diffused, the softer shadows become. This is also the cause of atmospheric perspective. Atmospheric Perspective is the viewable phenomenon of things getting bluer or less saturated and fuzzier in the extreme distance. The diffusion of light in the air is what we can sense, even if we are unaware of it happening. The ability to control this gives the artist explicit control over the feeling of a scene. We will keep these two qualities of mind when we talk about Time of Day and Mood.

Colored lights can be very powerful, but can also get out of hand very easily. When using colored lights, try to stay away from saturated and dark colors. That said there is always a time and a place for vibrant lights, just keep in mind that is not very natural.

The color of a light, on film, greatly effected by the balance of that film. Because in 3D graphics there is no film actually being exposed we need to simulate it. On a side note: It is a strange phenomenon that people perceive an image that has all the flaws, distortions and artifacts of film to be more "real" that a well light and clean render. So where does that leave us? Well, we try to approximate what the camera lens is seeing, in order to accommodate the tastes of our audience. Of course, a chosen style should prevail.

For simplicity sake we will focus on two different types of balanced film. "Indoor" or Tungsten-Balanced and "Outdoor" or Daylight. There are other kinds of film and gels and filters and post effects that all can contribute to the overall color of a scene. A good thing to keep in mind, is that the dominate light source in the scene should dictate the balance of the film. The balance that is referred to is on the Kelvin Scale. It is a scale that measures color temperature. The range of the Kelvin scale is from 0K - 10000K. The higher the temperature the bluer the color and the lower the temperature the redder the color. An Outdoor film would be balanced for 5500K and an Indoor film would be balanced for 3200K.

So what does the light balance of film mean to a CG artist? It means that in a "balanced" light set up, the dominant light source would be close to white, all others would range from warmer to cooler. For example: In a daylight balanced scene, the sun would be a very pale yellow and the light from the sky would be a light blue. You knew this already? Well how a bout an indoor scene lit with a torch near a doorway to the outside? With an Indoor balanced scene the torch would be a pale orange while the sunlight from the doorway would be bluish.

A final word about Quality and Color. These, like all the other principles that are being discussed in this guide, are only part of the equation and are in no way absolute. Let story and character drive your lighting set ups. Not the other way around.

We will talk further about overall lighting pallets in the Time of Day and Mood section. There we will go more in depth about tinting a scene to convey emotion.

Part 5 - Time of Day and Mood

To convincingly convey Time of Day and create a Mood all the principles, rules and tricks we know will now come into play. This is where it all comes together and stories are told. A well planned light set up will establish Time of Day, Seasons and even the Emotional State of the characters involved in a scene. In this Section we will discuss techniques used to believably create a scene that pushes forward and supports the story. Most likely the main light source of an outdoor scene is going to be the Sun. It is a well known fact that the Sun rises in the east, arcs through the sky and sets in the west. This makes the decision where to put the key light when the time of day is known. But, please don't be to strict a bout where the sun is placed tin the scene. Aesthetics and a well light scene are more important than a astronomically accurate representation of the sun. No one will notice if we fake the sun position if the scene looks good.

This image shows a possible representation of a day to night transition.

Morning light tends to be a light blue with a pale pink sky or fill. The shadows are long and crisp. The sun itself will be a very orange and fade quickly as it rises to more of a pale yellow. Light from the sun bends quite a bit as it travels through the atmosphere and it shifts color more and more as it nears the horizon. However, in most cases, there is very little atmospheric perspective visible during the very early hours of the day. This is due to the fact that the dust has literally had time to settle in the inactivity of the evening. Dawn has a distinctively different look than Sunset because of this. Emotionally the morning represents rebirth and optimism. A use of bright colors both in the light and shadow will bring across that feeling of crisp cool air of the morning.

As the day goes on and the Sun reaches its apex in the sky the rays of light are traveling through the atmosphere nearly perpendicular to the ground. This means that the light won't bounce around and bend as much and its light is closer to a bright white. The shadows are dark and colors seem muted in the bright light. The term "high noon" evokes a lot of feelings. There is nowhere to hide in the relentless rays of the bright daytime sun. In winter, however, the sun would be much lower and pushed more towards the blue.

Finally the sun begins to set and the color of the light becomes more and more red. The shadows stretch out and are blue or purple. Because of the activity during the day and the increase of particles in the air, sunsets are very orange and red. The hours preceding sunset are used in film quite often. It is because of the vibrant and rich colors that are present in the late afternoon.

The sun is gone and the stars and moon are the only natural light sources. Now that night has arrived this is no excuse to ditch color. . Nighttime can be full of color, just mostly blue. But if we accent it with warm manmade practical lights we can get a full and rich palette for our scenes. Also, keep shadows sharp and have a high key-to-fill ratio to enhance the feeling of night.

Part 6 - Quality of Light and Colour Balance

This image shows a possible representation of SUMMER.

I used a pale yellow key light with a bluish fill. I also added a bluish "sky" lightthat I placed directly above the scene.

This image shows a possible representation of FALL. I used a bluish key light with a reddish fill. I also added a bluish "sky" light that I placed directly above the scene.

This movie shows the transition between a typical studio set-up to one possible representation of a winter scene.

Showing the difference in season can be tricky. Of course, it is easier if we rely on some recognizable conventions. Most of the viewers will know these conventions, Winter is bleak and cool, Summer is bright and warm, so why not exploit that fact. The only people that have absolutely no clue what seasons are, are from southern California, but I am sure they have seen Fall and Winter on television.

Look at the accompanying images to get some inspiration to create your own seasonal scenes. Think about all the things that it takes to light a scene and try to apply them to the look you are trying to achieve.

Hopefully these tips and suggestions will jump start your curiosity. There are so many ways to light a scene, but as storytellers we must ask what is the best way to illuminate the character and the story.
Creating a specific Mood in a scene can be one of the most important thing a good lighting set-up can do. The ability to convey feeling with your lighting can greatly enhance the story and the understanding of a characters motivation. The are some "universal" color theories on the subject of color and emotion. Used wisely, these can be incorporated in to an intelligent color palette of your scene.

Kory Heinzen is a Production Ilustrator at PDI/Dreamworks currently working on Shrek 2. Although he was trained as a traditional illustrator he has always had a passion for digital media and is always looking for ways to bring his traditional skills to the 3D graphics world.

Visit his website to see recent work and projects.

Here are just a few of books that are available on this subject...

Painting With Light by John Alton

Film Lighting: Talks With Hollywood's Cinematographers and Gaffers
by Kris Malkiewicz, Leonard Konopelski (Illustrator), Barbara J. Gryboski

The Five C's of Cinematography: Motion Picture Filming Techniques
by Joseph V. Mascelli

Film Directing Shot by Shot: Visualizing from Concept to Screen
by Steven D. Katz

Lighting for Digital Video & Television
by John Jackman

Digital Lighting & Rendering
by Jeremy Birn, George Maestri (Editor)

The Art of 3-D: Computer Animation and Imaging, 2nd Edition
by Isaac Victor Kerlow

Inspired 3d Lighting & Compositing
by David A. Parrish

Cg 101: A Computer Graphics Industry Reference
by Terrence Masson

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