9

Choosing Colors for Realism 1401
Indoor and Outdoor Li ghting
Whether a scene is indoors or outdoors affects
your choice of material colors, just as it affects
the way you set up lights (page 2–1272).Full
sunlight is bri g ht and unidirectional. Most indoor
lighting is less intense and more even (that is,
multidirectional) than daylight. However , some
special indoor lighting (and nighttime outdoor
lighting), as for the stage, also features intense,
directional l ight.
Direct sun light has a yellow t int. Materials for
objects to appear in daylight should have a specular
color of a pale, unsaturated yellow (for example,
RGB values of 240, 240, 188). The ambient color
should be the complement of the specular: a deep,
dark purple with a hint of the diffuse color.
Materials for objects to appear under normal
interior lighting should ha ve a specular color that
is close to white. (O ur perception compensates
for the yellow or green tint that is often present in
artificial light.) The ambient color can often have
thesamehueasthediffusecolor,butwithadarker
value.
Materialsforobjectstoappearunderspotlights
should follow the general guidelines for daylight
materials. The specular color should match the
spotlight’s color, and the ambient color should
be a very dark value of the spotlight color’s
complementary hue, mixed with a bit of the
material’s diffuse color.
If you want to render an object under changing
lighting conditions, you can choose colors that are
acompromisebetweentheoptimalcolorsforeach
kind of lighting, or you can animate (page 2–1449)
the m aterial so that its colors change to suit the
changing light.
R epres enti ng Na tur a l M ater i al s
Outdoor scene with natural materials
Most natural materials have a matte sur face with
little or no sp ecular color. For natural m aterials
such as these, use the following guidelines:
• Ambi ent color : The ambient color depends on
whether the scene is indoors or outdoors, as
previously described.
• Dif fuse col or: Choose a color found in nature.
It is best to u se the observed color of t he object
itself, or a similar object.
• Specula r color: Make the specular color the
same hue as the diffuse, but with a higher value
and a lower saturation.
• Glossiness: Set the Glossiness to a low value.
Some foliage, bird feathers, fish scales, and so
on, are shiny. For materials such as these, set
the Glossiness to higher values. You might also
want to change the specular color so it’s closer
to the lighting color than the sur face’s diffuse
color.
Water is reflective, and is best modeled by a color
componen t in combination with a reflection map
(page 2–1699) or a water map (page 2–1683).
While metal is a natural material, its special visual
characteristics are most apparent when it has been
polished. Standard material represents this by