Autodesk LIGHTSCAPE, Manual

Page: 112 / 362

Using Materials 7
104
Lightscape
Color
To correctly set a material’s color, ask yourself these
questions:
Hue: What color is the material?
Hue controls the color of the material.
Saturation: How much color is reflected?
Saturation controls the degree of coloration of a
material. Increase the saturation to deepen the color
of the material.
You should not make a material overly saturated. As
saturation increases, the light bouncing from the
material is highly colored and, if the color value is
also high, the entire room takes on the color of that
material. If you want to use a material with highly
saturated color, but obtain too much color bleeding
in the radiosity process, you can reduce the effect of
this color on surrounding surfaces by adjusting the
material’s Color Bleed Scale. For more information,
see “Using Color Bleed Scale” on page 113.
Value: How much light is reflected from the
material?
Value controls brightness of a material.
It also controls the reflectance. Reflectance is the
amount of light energy that is reflected diffusely
from a surface. When you increase a material’s color
value, the material reflects more light.
Note: In general, the color value of metals tends to
be higher than that of nonmetals. The color value
of metals ranges from about 0.30 (tarnished
copper) to 0.9 (highly polished silver), while the
color value of nonmetals ranges from about 0.05
(coal soot) to 0.7 (white paper). For more informa-
tion, see Appendix A, “Light and Color.”
To obtain a proper radiosity solution, it is very
important that the reflectance of a material represent
a physically valid range for the type of material being
modeled.
If you make the color value of your material too high,
the solution looks washed out and processing time
increases significantly. If you want to display or
render a bright color while limiting the amount of
light reflected into the model, you can adjust the
material’s Reflectance Scale. For more information,
see “Editing Material Properties” on page 111.
Using RGB Color Values
It is usually easier and more meaningful to pick a
color using the HSV values, as these correspond to
important aspects of the color. You have the option,
however, to use RGB values that correspond to the
red, green, and blue wavelengths of the color
spectrum.
Each component of the RGB values provides the
color value for that wavelength of the color spec-
trum. For this reason, you should keep each of the R,
G, and B values within the appropriate value range
(0.05 to 0.7 for nonmetals and 0.30 to 0.9 for metals).
Note: You can also use a bitmap texture file to set
a material’s color. For more information on using
textures, see “Using a Texture Map” on page 114.
Transparency
Transparency determines how much light passes
through the material. The light hitting a material is
scattered and attenuated by the material based on its
transparency.
Transparency ranges from 0 to 1 where 0 is opaque
and 1 is completely transparent. All metals are
opaque, so their transparency is 0.
A material’s transparency and its color are related.
Consider a piece of stained glass. The light from a
stained glass window depends both on how trans-
parent the glass is and on what color it is. The same