Light and Shadow
Of
all the topics in traditional art, this is arguably the most important
due to its difficulty to master and importance to the final work. Light
and shadow give depth to and, as a result, define what we see. At its
simplest, light and shadow are easy to see and understand. Most of us
are familiar with shadow; our own shadow cast by the sun, making animal
silhouettes with our hands on the wall, or a single light source
shining on a sphere and the round shadow that it casts. That’s where
this book will start. Light and shadow quickly get more complicated,
and the examples in this book will get more complex as well. The book
will start with the ability to see and analyze light and shadow in this
chapter, move up to creating and tweaking light and shadow in Photoshop
using Layer Styles for the most part, and finally look at some basic
hand tweaking of light and shadow. If you desire to master the ability
to hand paint light and shadow on complex and organic surfaces, then
you are advised to take traditional art classes in illustration,
sketching, and painting.
We
all know that the absence of light is darkness, and in total darkness
we can obviously see nothing at all, but the presence of too much light
will also make it difficult to see. Too much light blows away shadow
and removes depth and desaturates color. In the previous section we
looked at how shape and form differ. We see that difference primarily
as light and shadow as in the example of the circle and a sphere. But
even if the sphere were lit evenly with no shadows and looked just like
the circle, the difference would become apparent when rotated. The
sphere would always look round if rotated, whereas once you began to
rotate the circle it would begin to look like an oval until it
eventually disappeared when completely sideways. In the previous
example, where a shape was cut into an image of rusted metal and made
to look like a metal space door using Photoshop Layer Effects, the
highlights and shadows were faked using the various tools and their
settings. In Figure 1-6 you can see the same door texture rotated from
front to side. Notice the complete lack of depth in the image on the
far right. The illusion is shattered.
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Figure
1-6: Here is the same door texture from the previous section. Notice
the complete lack of depth as we look at it from angles other than
straight on. The illusion of depth is shattered.
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Understanding
light and shadow are very important in the process of creating quality
textures. We will go into more depth on this topic as we work through
this book. One of the main reasons for dwelling on the topic is not
only due to the importance of light and shadow visually, but you will
see that many of the decisions that need to be made are based on
whether light and shadow should be represented using texture, geometry,
or technology. To make this decision intelligently in a serious game
production involves the input and expertise of many people. While what
looks best is ideally the first priority, what runs best on the target
computer is usually what the decision boils down to. So keep in mind
that in game development you don’t want to make any assumptions about
light and shadows--ask questions. I cover different scenarios of how
light and shadow may be handled in a game in this book. It can be
challenging to make shadows look good in any one of the situations. Too
little and you lack depth, too much and the texture starts to look
flat. Making shadows too long or intense is an easy mistake. And unless
the game level specifically calls for that, on rare occasion, don’t do
it. Technology sometimes handles the highlights and shadows. This is
challenging because it is a new way of thinking that baffles many
people who are not familiar with computer graphics. This method can
also be a bit overwhelming because you go from creating one texture for
a surface to creating three or more textures that all work together on
one surface. Naming and storing those textures can get confusing if you
let it get away from you.
Overall
you want your textures to be as versatile as possible and that
includes, to a great degree, the ability to use those textures under
various lighting conditions. See Figure 1-7 for an example of a texture
where the shadows and highlights have been improperly implemented and
one that has been correctly created. For this reason we will purposely
use highlight and shadow to a minimalist amount. You will find that if
you need more depth in your texture than a modest amount of highlight
and/or shadow, then you most likely need to create geometry or use a
shader—or consider removing the source of shadow! If there is no need
for a large electrical box on a wall, then don’t paint it in if it
draws attention to itself and looks flat. If there is a need and you
are creating deep and harsh shadows because of it, you may need to
create the geometry for the protruding element. You may find that as
game development technology accelerates, things like pipes, door knobs,
and ledges are no longer painted into the texture but modeled in
geometry. Many texture surface properties are no longer painted on.
Reflections, specular highlights, bump mapping, and other aspects of
highlight and shadow are now processed in real time.
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Figure
1-7: The crate on the left has conflicting light sources. The shadow
from edge of the crate is coming up from the bottom, is too dark, is
too long, and even has a gap in it. The highlights on the edges are in
conflict with the shadow cast on the inner panel of the crate, and they
are too hot, or bright. The crate on the right has a more subtle,
low-contrast, and diffuse highlight and shadow scheme and will work
better in more diverse situations.
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In
the rest of this book we will take various approaches to light and
shadow using both Photoshop’s Layer Effects to automate this process
and other tools to hand paint highlights and shadows. One of the main
benefits to creating your own highlights and shadows in your textures
is that you can control them and make them more interesting as well as
consistent. Nothing is worse than a texture with shadows from
conflicting light sources: harsh, short shadows on some elements of the
texture and longer, more diffuse shadows on others. See Figure 1-8 for
an example of this. The human eye can detect these types of errors even
if the human seeing it can’t quite understand why the image looks
wrong. One of the artist’s greatest abilities is not only being able to
create art, but also being able to consciously know and verbalize what
he is seeing. In Figure 1-9 you can see the various types of shadows
created as the light source changes. This is a simple demonstration. If
you ever have the opportunity to light a 3D scene or movie set, you
will discover that the range of variables for light and shadow can be
quite large.
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Figure
1-8: Here is a REALLY BAD texture created from two sources. Notice the
difference in the shadows and highlights. The human eye can detect
these errors even if the human seeing it can’t understand why the image
looks wrong.
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Figure
1-9: With one light source and a simple object you can see the range of
shadows we can create. Each shadow tells us information about the
object and the light source, such as location, intensity, etc.
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Highlights
also tell us a good bit about the light source as well as the object
itself. In Figure 1-10 you can see another simple illustration of how
different materials will have different highlight patterns and
intensities. These materials lack any texture or color and simply show
the highlights and shadows created on the surface by one consistent
light source.
For a more advanced and in-depth discussion on the subject of light and shadow for 3D scenes, I recommend Essential CG Lighting Techniques by Darren Brooker.
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Figure
1-10: With one light source and a simple object with various highlights
on it, you can see that the object appears to be created of various
materials. Keep in mind that what you are seeing is only highlight and
shadow. How much does only this aspect of an image tell you about the
material?
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