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1550 Chapter 16: Material Editor, Materials, and Maps
Diffuse group
Diff use Level—Diffuse Level (page 2–1489) controls
thebrightnessofthediffusecolorcomponent.
Range=0.0 to 1.0. Default=1.0.
Note: Because the material is energy conserving,
the ac tual diffu se level used depends on the
reflectivity and transparency, as discussed in the
introductory section, above.
Co lor—Controls the diffuse color (page 3–929).
The diffuse color is the color in direct ligh t.
Default=50% gray.
Roughness —Roughness (page 2–1490) controls
how quickly the diffuse component blends into
the ambient component. Range=0.0 to 1.0.
Default=0.0.
The diffuse component uses the Oren-Nayar
shading m odel. When the Roughness v alue
is 0.0 this is identical to classical Lambertian
shading, but with higher values the surface gets a
more “powdery” look, as shown in the following
illustration.
Left: Rou gh ness=0.0; Center: 0.5; Right: 1.0
Reflection group
Reflectivity—The overall level of reflectivity .
Range=0.0 to 1.0. Default=0.6.
The Reflectivity and Color values combine to
definethelevelofreflectionsaswellastheintensity
of the traditional highlight, also known as the
specular highlight.
This value is the maximum value; the actua l value
also depends on the angle of the surface and comes
from the BRDF cur ve. This curve (see BRDF
rollout (page 2–1554))letsyoudefine0–degree
reflectivity for surfaces facing the view and
90–degree reflectivity for surfaces p erpendicular
to the view.
Left:Noreflectivity,withapurelydiffusematerial
Center: Angle-dependent reflectivity, with 0–degree reflectivit y
of 0.1 and a 90–degree reflectivity of 1.0
Right: Constant refle ctivity, with both 0–degree reflectivity and
90–degree reflectivity of 0.9
Note: In the preceding illustration, the high
reflectivity automatically “subtracts ” from the
white diffuse color. If this didn’t happen, the
material would become unrealistically overbright,
and would break the laws of physics.
Co lor—The overall color of reflected ligh t.
Default=white.
Glossines s—Defines the surface “glossiness,”
ranging from 1.0 (a perfect mir ror) to 0.0 (a
diffusely reflective sur face). Default=1.0.
Left: Glossiness=1.0; Center, 0.5; Right, 0.25