16 ESSENTIAL CG LIGHTING TECHNIQUES WITH 3DS MAX
indoor shot if the main light source is a window. This also applies
conversely: indoor film is generally used for outdoor night scenes,
as the dominant light in this situation would be artificial lights.
For an outdoor rendering, if you wanted to mimic daylight-
balanced film, you’d start with a color balance of 5500 K. Your
light representing the direct sun, depending on the time of day,
would, according to Table 2.01, have a color temperature of
somewhere between 4300 K and 5000 K. Being slightly less than
your chosen color balance of 5500 K, you’d give this light a
yellow tint, with the saturation increasing the lower the value.
The light from the sky would be given a saturated blue tint, as
its color temperature is much higher than your 5500 K color
balance. However, the saturation of these tints is something
ultimately left to your own assessment. Furthermore, in reality
outdoor illumination is made up of many more colors, due to the
way in which the sun’s light reflects off objects in the
environment, bringing into the scene light tinted with the colors
of these reflecting objects. Take a look at your scene and the
principal colors of the largest surrounding objects. For example, if
your scene were set against a backdrop of a large brick wall, the
red color of the light bouncing from the bricks would have to be
imparted to your lighting scheme.
For lighting scenarios where the dominant light source was
artificial, the same principles would apply, though you’d be
working with a color balance of 3200 K to mimic tungsten-
balanced film. The lights that would have a lower temperature
and thus have to be given a yellow tint would now be things like
domestic lights. Direct sunlight, however, would now be of a
higher color temperature and thus would be given a blue tint,
unless it was sunrise or sunset. The colors of the light bouncing
off the walls, floor and ceiling of the environment would still also
have to be taken into consideration.
One final thing of note is fluorescent lighting, which has a high
color temperature range – from 3200 K to 7500 K. Whilst this is
straightforward with a 3200 K color balance representing
tungsten-balanced film – all fluorescent sources invariably should
be tinted blue – with 5500 K as a chosen color balance, should a
fluorescent light be tinted blue, yellow or red? The answer
depends on what atmosphere you’re trying to create. However,
for all situations, no matter what the color balance selected,
fluorescent light invariably looks more obviously flourescent when
it has been tinted green, as this color emphasizes the artificial
light. Shots from movies using this type of lighting will often be
graded to look more green to emphasize this artificial atmosphere.
There is certainly no such thing in photography as correct results
and the hue, saturation and brightness of any light will appear
differently for each individual, producing different colors in the
CHAPTER 2 > A LITTLE LIGHT THEORY 17
print. This is due to a number of factors: the color balance of the
film (which is invariably daylight-balanced); the tint of the flash
bulb used; and the filters used by the processing laboratory.
Indeed, just as sometimes happens in the world of photography,
you might want to throw this whole system out of the window
and instead concentrate on a more stylized look. In this case the
tinting of lights is still best done by eye, but as with all things,
it’s ideal to understand how to best use the rules of color
balance before you can break them.
The behavior of light
Light obeys a whole heap of rules, some relevant for
understanding lighting in CG, some not so relevant. One rule that
certainly is very pertinent to the world of 3D is the inverse square
law. This explains how light fades over distance. Indeed, this
law is applicable to all types of radiation and it is perhaps most
easily explained by considering heat. If you walked slowly
towards a fire, you would feel yourself getting gradually hotter.
However, the rate at which you would get hotter would not
increase uniformly as you approached; you would feel a slow
increase early on, but as you got closer and closer to the fire,
you’d feel a very rapid increase in heat. This is the inverse
square law in action.
The way in which light fades from its source also obeys this law.
The light’s luminosity (the light’s energy emission per second)
does not change; what alters is the light’s brightness as
perceived by the viewer. As light travels further away from its
source, it covers more area and this is what makes it lose its
intensity, fading according to the reciprocal of the square of the
Figure 2.08
The inverse square law in action
18 ESSENTIAL CG LIGHTING TECHNIQUES WITH 3DS MAX
distance. For example, at two meters away from the source it has
lost a quarter of its intensity compared with its intensity at one
meter from the source. This is simply because the area it has to
cover is four times bigger, so the light is spread over four times
the area. At three meters, it’s lost a ninth of its intensity
compared with its intensity at one meter, because it is spread
over nine times the area. This law is important in 3D because
this is how real lights behave, and though 3D solutions have an
option to turn this behavior on, most in fact have this off as a
default unless you are working with photometric lights and
radiosity, but we’ll go into this in more detail when we examine
the anatomy of a light later in this section.
Light also obeys the simple law of reflection, which you might
remember from physics class. This explains how light is reflected
from a surface. The law states that the angle of reflection equals
the angle of incidence, which is measured relative to the
surface’s normal at the point of incidence. The simulation of this
law in CG takes place using a rendering process called
raytracing, which simulates accurate reflections and refractions.
This second term, refraction, describes how light bends and
obeys Snell’s law, which concerns transparent and semi-
transparent objects. Basically this determines the extent of
refraction when light passes between different materials. This
bending causes the distortion that you can see by looking at a
lens. There is no need to explain Snell’s law itself, it is simpler to
explain what determines how much the light will bend: the
index of refraction.
This number is calculated by taking the speed of light in a
vacuum and dividing it by the speed of light in a material. Since
light never travels faster than in a vacuum, this value never goes
below 1.0 for basic applications. At this value there will be no
bending of light and as this value increases up to 2.0 and
Table 2.02
Typical Index of Refraction (IOR) settings
Material IOR
Air 1.0003
Alcohol 1.329
Water 1.330
Ice 1.333
Glass 1.500
Emerald 1.570
Ruby 1.770
Sapphire 1.770
Crystal 2.000
Diamond 2.419
CHAPTER 2 > A LITTLE LIGHT THEORY 19
Figure 2.09
Glass is rendered with an IOR of 1.5
Image courtesy of:
Antoine Magnien
[email protected]
20 ESSENTIAL CG LIGHTING TECHNIQUES WITH 3DS MAX
beyond, the amount of distortion will increase. Table 2.02, on
page 18, lists the index of refraction for several materials, with
Figure 2.08 demonstrating how these values appear once
rendered in 3ds Max.
Understanding the qualities of light
The eye is one of the most incredible and intricate of our organs;
yet seeing is so undemanding that it’s very rarely that we tend to
give this ability a second thought. We are so used to looking in
fact, that we can easily spot when something, especially in CG,
does not look quite right. To ensure that your lighting efforts in
3D appear convincing, there are several characteristics that make
a light source look real, and these qualities of light must be
thoroughly understood and simulated in 3D.
You might have at some point come across the term ‘quality of
light’, which is a subjective term that means different things to
different people. If you gave several Directors of Photography
(DoP) the task of lighting a movie scene, you’d undoubtedly get
very individual and different results, as diverse as the DoPs’
imaginations. First, considering the space that the DoP has to light,
each would refer to the script and consider the events, emotions
and personalities of the story before arriving at a solution, or
possibly even several potential approaches towards a solution.
If you then examined each individual’s lighting schemes, you’d
no doubt get a wide range of variations that might go from the
gritty and realistic to the sumptuous and glamorous. Depending
on the nature of the scene, the results might equally be slick and
Figure 2.10
Hard light is overused in CG due to
it being closer to most 3D
applications’ default settings
CHAPTER 2 > A LITTLE LIGHT THEORY 21
clean or futuristic and stylized. The lighting does not have to
follow the script literally: a miserable situation placed within a
sunny scene might seem more compelling, particularly if this
irony is reflected elsewhere in the script. Matching the lighting to
a story can be done in a practically infinite number of ways, and
each DoP’s set-up would be quite individual.
If you then attempted to sit in front of these different versions
and categorize the qualities of the lighting in each instance,
you’d end up with a long list indeed. If you examined the work
of Darius Khondji, for instance, you’d undoubtedly dwell on the
way the soft light wraps around its subjects and the way this
contrasts with other more hard light sources. Khondji has
become renowned for his expressionistic look and his use of soft
lighting techniques in such films as The Ruins, Delicatessen, The
Beach, Se7en, which featured a bleak color-noir style, and Evita,
for which he won an Academy award for Best Cinematography.
Khondji’s soft-lit style became fashionable due partly to the
advances in lighting equipment.
However, were you to view the lighting efforts of not just
Khondji, but the other DoPs you’d given the same task to, you’d
find yourself describing not just the soft and hard aspects of
lights. Your descriptions would also concern the intensities and Figure 2.11
colors used, the shapes and patterns that the lights form, and Soft light is a little more difficult to
the way in which these shadows move. You could go on to achieve, but looks much better
22 ESSENTIAL CG LIGHTING TECHNIQUES WITH 3DS MAX
describe the motivation behind the light, whether it’s natural or
artificial and whether it relates to a visible source in the scene.
However, if you attempted to categorize these many different
descriptions under as few headings as possible, you’d probably
come up with something based around the following: animation,
color, intensity, motivation, shadows, softness and throw.
You might come up with more or less categories, depending on
how much you think that shadows and throw were part of the
same thing, or whether you think animation is a quality of light.
Anyway, looking at these rough categories, if you tried to put
them into some kind of logical order, you might put intensity first,
followed by color, softness, animation, shadows and finally
motivation. This would depend on what your role was; if you
asked Darius Khondji, he’d probably put softness nearer the top
of the list. However, these have been ordered as such from the
point of view of a CG professional.
Intensity
The primary reason why intensity is top of our list is because of its
role as one of the most obvious and perceptible qualities of light.
The light with the strongest intensity in a scene is known as the
dominant light and will cast the most noticeable shadows.
Indeed, in cinematography’s established three-point lighting
system, it is this dominant light that is considered the key light.
This system of lighting is heavily applied to CG and is described in
considerable depth in the following techniques section, so don’t
worry too much if you don’t know about three-point lighting yet.
Historically there has been a considerable difference between
cinematography and CG where light intensity is concerned. In
the world of film, whether you’re dealing with a cave scene lit
by the light of a single flaming torch, or a beach scene lit by the
brightest sunlight, the camera’s exposure settings are adjusted to
allow it to record properly in these dim or bright conditions. In
CG, until recently there were no exposure settings as such, so
the intensity of a light source directly affects the final output’s
brightness and it has been this that is altered, rather than the
camera’s exposure. However, exposure controls are now common
in 3D applications, giving a similar type of control to how tone
levels are mapped to a display range.
Even with these controls now in place, just as a cameraperson
would have to change the exposure settings on the camera
depending on the location, a lighting artist will still have to adjust
the intensity of the lights depending on their context within the
shot. For example, if the flaming torch were carried out of the
cave to a sunlit beach, its intensity might have to be reduced to
make the scene appear realistic and correctly exposed, but new
exposure controls go a long way to addressing this.
CHAPTER 2 > A LITTLE LIGHT THEORY 23
Figure 2.12
Color plays a big part in lighting
Image courtesy of:
Patrick Beaulieu
www.squeezestudio.com
The intensity of a light is controlled by its color and its multiplier
or brightness value, along with its attenuation. All light in the
real world falls off, as previously discussed, at an inverse square
rate, that is its intensity diminishes in proportion to the reciprocal
of the square of the distance from the light source.
In CG, attenuation can be dealt with in several ways, with
inverse square decay one of the options. This is often too
restrictive for CG work, so a start value allows you to specify
where the decay actually starts, which allows for more realistic
results. It’s worth noting that light obeying the inverse square
rule never actually reaches a zero value, so it’s worth setting the
far attenuation value to a distance where the illumination
appears to have ended to avoid unnecessary calculations. This
value, along with an accompanying one that dictates the near
attenuation point, can be used along with linear attenuation to
give a very predictable falloff from the near to the far value.
Alternatively, attenuation can be turned off entirely, making the
distance to the light irrelevant, as the illumination from such a
light would be constant.
24 ESSENTIAL CG LIGHTING TECHNIQUES WITH 3DS MAX
Color
As a visual clue to the type of light source or the time, season
and weather being represented outside of a scene, color is
incredibly important. The similarities and differences of lighting
colors within a scene will help determine its mood, with more
neutral colors giving a more somber tone, for example. Colors also
have emotional properties and different people have different
reactions to a color depending on the associations that they make
with the color. However there are color families that denote and
evoke a similar response in nearly all people. The use of cool
colors versus warm colors for example has been used by artists
for centuries to denote obvious feelings to a broad audience.
Color is extremely useful in reinforcing the type of light source
that is being represented, and though this will vary due to the
color balance that you may have selected, yellow to orange light
is typical of domestic lighting. Place a blue light outside a
window and the viewer will associate the light coming inside the
room from this source with the light coming from the sky.
Whilst cameras and film are color balanced for different
environments and their light types, the color of light sources in
CG needs to be altered depending on not only what type of light
you are representing, but also what mood you are attempting to
portray. Blue light can help to paint both a moody, unhappy
scene and a calm serene one, whilst red is often used to signify
danger or passion. Consider also the symbolisms that different
colors have become associated with – green recalls such things
as peace, fertility and environmental awareness on the positive
side, but greed and envy on the negative side. Its use in lighting
can also reinforce a sense of nausea in a scene, as it imparts a
very artificial, almost chemical feel to the light. For all these
reasons, color is a sizable consideration in lighting design.
Softness
Though soft light is widespread around us in the real world, and
thus is also widespread in the world of cinematography, in CG it
appears nowhere near as often as it should. Though it is not
difficult to reproduce the full range of light from hard to soft in
all 3D applications, the fact that most default settings produce
fairly hard results means that we see more crisp-edged shadows
than we should in CG productions. We come across hard light in
real life comparatively rarely and few of the light sources that we
come into contact with exhibit the sharp focus that we so often
see in CG. The sun can cast this kind of light, but a lot of us are
used to seeing its light diffused through a layer of clouds or
pollution. Bare light bulbs, car headlights and flashlights can also
produce the crisp shadows of hard lights, but most lights give
soft-edged shadows.
CHAPTER 2 > A LITTLE LIGHT THEORY 25
Figure 2.13
Throw patterns break up a light
into interesting patterns
Throw
The manner in which a light’s illumination is shaped or
patterned is described by the term ‘throw’. This breaking up of
the light can be due to the lampshade of a domestic lamp, blinds
or net curtains on windows or clouds in the sky. The approaches
to recreating this aspect of light in 3D can vary from modeling
the actual object causing the throw effect, which might be likely
in the case of a light fitting, to the use of texture maps which
cause the light to act like a projector, which would be more
applicable for light filtering through leaves or foliage.
These types of texture maps mirror the use of a cookie or gobo
(also known as a cucoloris or go-between) in cinematography.
These objects are placed in front of studio lights to break the
light into interesting patterns of light and shadow. In CG the use
of texture maps acting like cookies generally involves a grayscale
texture map, where the amount of light allowed through depends
on the grayscale value: at one extreme, pure black blocks all light
and at the other 100% white lets all light through.
Physically placing objects in front of lights works in the same
manner as using cookies, and this practice is often used with
things like venetian blinds. However, if the window itself were
not actually visible in the rendering, it might be more efficient to
use a texture map acting as a cookie.
26 ESSENTIAL CG LIGHTING TECHNIQUES WITH 3DS MAX
Animation
This might not be a quality that you immediately associate with
light, especially if you were thinking about photographs or
paintings, but animation is a quality of light that is common to
winking car indicators, flickering neon signs and fading sunlight.
Think of several different instances where a light is changing
somehow and you can see that when it comes to lights,
animation covers color, intensity, shadows and other attributes.
Furthermore, the light can actually physically move, in the case
of a car indicator, for example, and the objects that a light
illuminates can also move, causing moving shadows to appear.
Animating a light’s parameters to simulate the flickering of a
neon sign, as we’ll do in chapter 9, can introduce a gritty sense
of location. Merely turning the intensity of a light up and down
really quickly and abruptly makes a light appear to flicker; this is
one of the more common ways of animating a light’s parameters
and one that we’ll use when we come to designing the neon
lighting later. Animating the color of a light can help to produce a
flickering fire effect, especially when coupled with an animated
intensity value. This is also true for televisions, which cast a
Figure 2.14 similarly varying light on a scene.
Logical lights are visible in a scene
Though animation might not be considered one of the primary
Image courtesy of: qualities of light, what it can bring to a scene in terms of
Platige Image: Fallen Art atmosphere cannot be ignored. For instance, a light bulb
www.fallen-art.com swinging from the ceiling will create the feeling of movement –
www.platige.com from the gentle swaying of an outdoor light in the wind to the
CHAPTER 2 > A LITTLE LIGHT THEORY 27
sickness-inducing swaying that might be experienced if this light
were in a room on board a ship. Moving objects in front of a light
to produce dynamic shadows can add a great deal to a scene, in
the way that a tree swaying in the wind would cast interesting
shadows through a window.
Shadows
Shadows play a massive role in describing a light, and this is an
area that we will go into in much greater depth in a couple of
chapters’ time. Shadows add to a scene’s realism, consistency,
relationships and composition. Rather than thinking of shadows
as something that things get lost in (though this can be very
useful for hiding imperfections), shadows actually show us
things that otherwise would be impossible to see. Arguably,
designing shadows is as significant a task as designing the
illumination in a scene, so important is their role. You will find
that when you get down to setting up your lighting schemes in
3D, a huge amount of time will be spent on shadows. You’ll face
choices as to which algorithms to use to generate both hard and
soft shadows, and how to do this in the most efficient manner
possible. In fact this is such a big subject that the whole of
Chapter 4 is dedicated to this issue.
Motivation
Lights can be categorized by how they operate in the scene in
terms of their motivation. Lights will sometimes be referred to as
logical, if the light forms part of the logically established sources
that are visible or implied within the scene. Logical lights can
represent an actual source such as a table lamp, or they can
represent the illumination from outside a window. These lights
are also called practicals in the theater and film industry.
The placement of lights can also be motivated by purely aesthetic
reasons. If a light has been placed simply because the effect it
produces is pleasing, then this can be described as a pictorial
light. Pictorial lights are often needed, as placing only logical lights
can result in a very uninspiring look and it’s generally the pictorial
lights that introduce the drama and create the emotional link with
the audience. Most people looking at a CG production, however,
won’t even consciously consider your lighting at anything
approaching this level, but this is one of the keys to good lighting;
if it plays the emotional role that it is designed to without drawing
attention to itself, then it has certainly succeeded.
By looking at light in terms of these different qualities, we can
begin to learn how to break it down into its component parts and
start to be able to record its essence. This is the first step towards
seeing light, which is the key to being able to light a scene to
underscore and show off the hard work of everyone involved.
CHAPTER 3 > CG LIGHTS EXAMINED 29
‘A picture must possess a real power to generate light and for a long time now
I've been conscious of expressing myself through light or rather in light.’
Henri Matisse
3
Lights in CG
L ighting a scene is vastly different from merely illuminating it.
All that you need to do to illuminate a scene is create a
single omni light and it’s illuminated. Lighting is a different
matter entirely, relying on the careful reasoned positioning of the
various individual sources that make up a lighting scheme.
Every one of your lights should be placed where it is for a
specific reason, with the lighting scheme built up steadily and
purposefully. As such, you should be able to explain the role of
each light in the overall set-up, which should be balanced, with
each of these sources playing a harmonious part in the
cumulative solution, rather than battling against each other. The
lighting scheme should emphasize the 3D nature of the medium
of CG, showing off the 3D forms to best effect when rendered.
You will never be able to do this by using omni lights every time, Image courtesy of:
and as such, a good understanding of the different light types Marcin Klicki
available and their characteristics is very important. www.bearsfromwoods.com
30 ESSENTIAL CG LIGHTING TECHNIQUES WITH 3DS MAX
Two categories of lights are provided within 3ds Max. If you go to
the Create tab and click on the Lights button, the drop-down
below displays two options: Standard and Photometric. Standard
used to be the default option, until 3ds Max 2009 and these lights
were more commonly used, but particularly with the move away
from the scanline renderer towards mental ray. Photometric lights
should now be considered as important to learn, if not more so.
This is not to say that standard lights should be forgotten about,
far from it! They are very versatile and can be made to simulate
any type of light from the sun to a desk light, and it’s this
versatility that makes standard lights so attractive. The color of
light, its decay and intensity; all of these things and more can be
controlled to act as the lighting artist requires. Standard lights are
also comparatively quick to render, something that is always a
consideration when working in context of production schedules.
Photometric lights, on the other hand, are less flexible. This you
might think is not a good thing, but this is their very advantage.
Unlike standard lights, photometric lights are based on the real
world of physical lighting and are built around the parameters of
light energy. As such, photometric lights use real-world
parameters such as distribution, intensity and color temperature.
This makes them very attractive for users who are looking for
ultra-realistic and physically-accurate renderings (so accurate
that lighting analysis is also possible).
Though these lights can be used with the scanline renderer,
particularly within the two advanced lighting modes that the
scanline features – Radiosity and Light Tracer – these two modes
are gradually becoming obsolete due to the development effort
being put behind mental ray. Radiosity is the scanline mode
which photometric lights operate best within and though it is
relatively processor-intensive and relatively slow to render, it is
simple to set up and the results can be very realistic, which is
part of the appeal. Within both the Standard and Photometric
light categories there are also lights designed exclusively for use
with mental ray, though these aren’t necessarily always the best
choice when working with this renderer. We’ll cover these at the
end of the sections on standard and photometric lights, and we’ll
go into much more detail when we look at working with this
renderer in chapter 11.
Standard lights
As we’ve already mentioned, flexibility is what makes standard
lights so attractive. Though radiosity techniques are capable of
beautiful and highly realistic results, the professional lighting
artist will often work using the standard lights alone, for several
reasons. The main rationale behind using standard lights is that
CHAPTER 3 > CG LIGHTS EXAMINED 31
Figure 3.01
Omnis and spots combined to
make a simple lighting fixture
they can be easily controlled and adapted to produce any style of
lighting and their controls allow the lighting artist to tightly
streamline their performance, especially at render time.
Omni lights
Though referred to as omni lights by 3ds Max users, other 3D
packages call these lights point lights or even radial lights. These
names help to explain how omnis behave because whatever they
are named in a particular application, these lights provide a point
source of illumination that shoots out radially from a single
infinitely small point. Due to the omnidirectional manner in
which these lights distribute their illumination through space,
they are the easiest light to set up, but in the real world you’d
struggle to find a light that acts in this manner, beyond a star, or
possibly a candle flame or firefly. Most lights in reality don’t emit
light evenly in all directions, especially the electrical lights that
they are often used to represent, which you can see by looking
at any light bulb around you.
There are of course several options for adapting omni lights to
work in this manner. You can place the omni within a
geometrically modeled light fitting, as in Figure 3.01, and turn on
the light’s shadow-casting function, though as you’ll discover in
the next chapter, the generation of shadows is the most
computationally-intensive part of rendering a light, so this is not
always the best option. Alternatively, you could use a bitmap as
a projector, which acts as a throw pattern, restricting the
emission of light. However, omni lights are perhaps best used to
provide fill lighting, and for this purpose this type of light can be
very useful indeed, as we’ll discover in later chapters.
32 ESSENTIAL CG LIGHTING TECHNIQUES WITH 3DS MAX
Spots
No confusion with names here, a spot is a spot in any 3D
package, and is the basic building block of a lot of lighting
situations. This is due to the fact that a spotlight is eminently
controllable in terms of its direction. Spots cast a focused beam of
light like a flashlight beam, and behave as in figure 3.02. Like
omni lights, spots emit light from a single infinitely small point,
but unlike omni lights, a spot’s illumination is confined to a
cone. As such, spotlights need to be aimed and this can be done
in several ways. One method is to position the light freely and
rotate it until it’s aimed correctly, which might not be the
simplest method, but is perhaps closest to how a real-world light
is aimed. A method that often proves itself to be more useful
involves giving the light a target object, so it remains facing this
no matter how the light is oriented.
As well as being able to manipulate a spotlight’s orientation, you
can also control its cone, which is defined by two angular values:
one defines the hotspot and the other controls the falloff. The
light’s intensity falls off gradually from 100% at the hotspot angle
to 0% at the falloff angle that defines the very edge of this cone.
Varying the amount between these two values controls the
softness of the light at this boundary edge of the cone. With a
small difference between these two values, the light will appear
in a sharply-defined circle, and as these values get further apart,
the light’s edge will get softer and softer. When given a really
soft edge, a spot will lose its defined edge and the location of the
light itself will become ambiguous, which can be a very useful
Figure 3.02 (above) tool, effective for subtly providing fill light to a specific region.
Target objects allow spotlights to
be aimed most conveniently
Figure 3.03 (right)
A spotlight’s cone can be adjusted
to give soft or hard falloff of light
CHAPTER 3 > CG LIGHTS EXAMINED 33
Spotlights will play a major role in the design of many lighting
schemes due to their controllable nature. The fact that they can be
easily targeted, given a falloff that can range from the crisp and
hard to the soft and subtle, makes them an obvious choice for a
huge amount of lighting tasks.
Direct lights
If you placed an omni relatively close to one or more objects, you
would see that the shadows cast by these objects would depend
on their relative position to the light source. Move the light
further away and you would see the shadows becoming
increasingly parallel. Move this source an infinite distance away
and the light source would cast parallel rays. Whilst even the sun
is not far away enough to cast totally parallel light, to all intents
and purposes it does, as this is how it appears to the naked eye.
This then is the role of a direct light: to cast parallel light rays in
a single direction. It is unsurprising then that these lights are
used primarily to simulate sunlight. These types of lights are
eminently simple to control: since the parallel light does not vary,
its position does not matter, only its rotation does, which is
controlled like a spot light by rotating the light itself or by moving
the object to which it is targeted.
However, this type of light should not just be confined to sunlight.
Direct lights are also often used for fill lighting, which is secondary
lighting that complements a scheme’s main light and is something
we’ll go into in more detail in the subsequent techniques section.
Direct lights are a good solution to modeling ambient light, which
can be thought of as a general light with no discernable source or
Figure 3.04
The direct light is the building
block of a lot of lighting scenarios
34 ESSENTIAL CG LIGHTING TECHNIQUES WITH 3DS MAX
direction, which is the result of light scattered off a scene’s
surfaces. This type of light is most noticeable in exterior scenes,
when the sky’s broad lighting produces an even distribution of
reflected light to surfaces not in direct sunlight. Actually modeling
ambient light using lights is far better than expecting 3ds Max’s
ambient light controls to do this, due to the way that directional
light can provide even illumination to large areas.
HDR maps
Skylights
High Dynamic Range images,
rather than using single Better still for this type of light is the Skylight light type, which
integer values between 0 and acts as a dome above the scene and models daylight, which can
255 to represent R, G and B be thought of as the light scattered through the atmosphere. This
values feature non-clamped light can be used with the scanline renderer, where it is capable
colors, which gives the of casting soft shadows. It is also designed to be used with one
renderer a far higher range of of 3ds Max’s two Advanced Lighting modes: the Light Tracer.
luminance values to work with.
This means that a whole range We’ll go into this in more detail in the next section on techniques,
of whites, from fully- but it is enough to say at this stage that the Light Tracer is
illuminated paint to the designed to be used in exterior scenes, where it produces the
superwhite of the sun itself can color bleeding associated with Global Illumination, but unlike the
be accurately represented. other Advanced Lighting mode – Radiosity – it does not calcuate
a physically accurate lighting model. Like Radiosity, this mode is
The HDR images in this book also a little long-in-the-tooth compared with mental ray. This can
were provided by Sachform. be a well-suited solution for outdoor scenes, where the daylight
www.sachform.com component can be quickly set up without the computational
demands of radiosity. The skylight has few controls besides the
color of the sky and the intensity, but notably a map can be
assigned to the skylight’s color and particularly good results can
be achieved using HDR maps, which we’ll go into in more detail
in the radiosity chapter in the next section.
Figure 3.05
Area lights provide a light with
physical size and hence realism
CHAPTER 3 > CG LIGHTS EXAMINED 35
Area lights Figure 3.06
Cylindrical area lights have obvious
As we have already discovered, in the real world there is no such applications for some light fixtures
thing as a point light, whose illumination comes from an infinitely
small light source. Real life light sources invariably have a
physical size. Area lights provide a light type with size (or even
volume), from across which light is emitted, providing a far more
realistic solution for depicting everyday light fittings.
The larger your area light, the softer the shadows will become
and the more pervasive the illumination – the light will begin to
surround objects that it is bigger than due to the source’s size
and the way it reaches over them. Conversely, if the same light
was made increasingly smaller, its shadows would become
gradually less soft until they eventually become hard-edged and
crisp. At this point the area light would have been scaled down
to a small enough size to start acting as a point light.
Area lights make for very believable lights and are capable of
realistic results, but their downside is that they can be quite
computationally intensive and take a lot of time to render. As
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