Surfaces
Very basically, there are three surface properties whose appearance is due to inter-reaction with light:
1.)Constant-Also called luminance, self-shading, ambient glow. This parameter controls how much of a base coat of illumination an object has. Most often, a slight amount of Constant shading goes into the overall appearnace of an object to make it look real (because except for my closet upstairs, nothing is totally without illumination in the universe.
2.)Diffuse-Also called roughness. This parameter controls how much illumination scatters when it hits the surface of an object. Indirect lighting in a house is the product of diffuse lighting, as is something such as a tennis ball.
3.)Specularity. Also called shineness, reflectivity. This parameter controls something called the mirror angle of light; how much light accumulates on a smooth surface into a highlight and reflects back to the camera (the viewer).By mixing amounts of diffuse and specular surface properties, you can create a plastic look (rough+specular), and metal (smooth+specular). As smoothness approaches 100%, the object takes on the color of the scene's illumination, and loses its native color, and generally will not take on shadows.
Transparency is a separate shading function which denotes the amount of light that passes through an object. Do not mistake Transparency for invisibility, however; a transparenct object can still show specular highlights.
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