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1400 Chapter 16: Material Editor, Materials, and Maps
the light is attenuated. Full intensity is the
light’s Multiplier value t imes the value of the
face’s surface color. The Multiplier value
is 1.0 by default; the surface value is the
Value component of the surface color’s HSV
description (page 3–1001).Astheangleof
incidence increases, the intensity of the face
illumination decreases.
Angle of incidence affects intensity.
• Dist ance: Lig ht diminishes over distance. This
effect is known as attenuation (page 3–912).By
default, attenuation is tur ned off, but you can
turn it on and specify the distance over w hich
it operates.
Light s a nd the Component Colors of a
Standard Material
As the names of a standard material’s color
components (page 2–1399) imply, the kind of light
that strikes a surface w ith a material determines
how the surface appears when it is shaded.
• Am bient color appears where the surface is lit
by ambient light alone (where the surface is in
shadow).
• Diff use color appears where light falls directly
on the surface. It is called "diff use" b e cause
light str iking it is reflected in various directions.
Highlights, on the other hand, are reflections of
light sources.
• Specular highlights appear where the viewing
angle is equal to the angle of incidence.
Glancing highli g hts appear where the angle of
incidence is high, relative to the observer or
camera (that is, the li g ht ray is nearly parallel
to the surface). Shiny surfaces u sually have
specular highlights. Glancing highlights are
characteristic of metallic surfaces.
Some surfaces are completely reflective, or
nearly so. These reflect their environment
as well as the light sources that illuminate
them. To model such surfaces, you need to use
reflection mapping (page 2–1699) or ray tracing
(see Raytrace Material (page 2–1512)).
The three color componen ts blend at the edges
of their regions. Between ambient and diff use,
the blending is calculated by the shader. Between
diffuse and specular, you set the amount of
blending by using the standard material’s highlight
controls.
Choosing Color s for R eal is m
Materials add greater realism to a scene only if you
choose their colors and other properties to appear
like real-world objects. This topic presents some
general guidelines for choosing standard material
colors. When possible, you should also observe
colors in t he objects you are modeling, especially
under different lighting conditions.
For objects on which you want the viewer to
focus attention, an unmapped standard material
doesn’t often provide the level of realistic detail
you probably want. However, for distant and
peripher ally visible objects, as well as some kinds
of real-world materials, such as molded plastic,
an unmapped standard material can work well.
Keeping the number of maps to a minimum can
helpkeepdownthefilesize.