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Q:
Explain diffuse factor, specular factor, and mirror
factor (Reflectance Tab)?
A:
On the Reflectance tab within the Material Editor, you
may see "diffuse factor", "specular factor",
and "mirror factor" depending on the current
material type you have selected. These factors can often
be confusing - especially the difference between specular
and mirror.
Diffuse
factor corresponds to the amount of light reflected
in a diffuse manner - a Lambertian reflection. Keep
in mind, that this is a multiplying factor.
For example, if the current color of the material (for
example "Beige") has a reflectance of 0.6
(60%), a diffuse factor of 0.50 will make the effective
reflectance 0.3 (30%). You'll note that the color
of the material becomes darker to indicate this. Setting
the diffuse factor to 1.0 is valid, and would result
in an effective reflectance of 0.6 (60%) in this example.
Specular
factor corresponds to the amount of light reflected
in a specular manner (much like a glossy or mirrored
surface). This too is a multiplying factor based on
other current material properties - much like the diffuse
factor. Mirror factor represents the
contribution of light reflected directly along the mirror
angle. In practice, the mirrored contribution is a portion
of the specular reflectance - just along the mirror
angle. The use of mirror factor separate from the specular
factor allows you to control how much a material will
preserve "images" in reflections.
This
issue of three reflectance components is also described
in the following NIST article
by Kelley, Jones, and Germer. In the article, the three
components are described as diffuse, specular haze,
and specular. The latter two correspond to specular
and mirror within Lumen Designer.
Q:
How do I set the effective reflectance on in a paint
material?
A:
After selecting the paint you desire you will assign
the color in the Color Tab. Next adjust the diffuse
factor on the Reflectance Tab. As you toggle the arrows,
you want to keep an eye on the effective reflectance,
which is located below the material name on the left
hand side. |
