[WelmanArch]

Here's some definitions of the material options.

Specular:
Latin specularis of a mirror, from speculum of, relating
to, or having the qualities of a mirror

Reflectance:
The fraction of the total radiant flux incident upon a
surface that is reflected and that varies according to
the wavelength distribution of the incident radiation

Transmittance:
The fraction of radiant energy that having entered a
layer of absorbing matter reaches its farther boundary

Attenuation:
To make thin or slender;
to lessen the amount, force, magnitude, or value of;
to reduce the severity, virulence, or vitality of

Roughness:
marked by inequalities, ridges, or projections on the surface

Lambert (Lambertian):
The centimeter-gram-second unit of brightness equal to the
brightness of a perfectly diffusing surface that radiates
or reflects one lumen per square centimeter

Anisotropic:
Exhibiting properties with different values when measured
in different directions

Bump:
A relatively abrupt convexity or protuberance on a surface

If someone would like to post something further on what each of these do to the basic materials types that would be fantastic.

Jamie