A second surface type is called a specular reflector.
When we look at a shiny surface, such as polished metal or a glossy
car finish, we see a highlight, or bright spot. Where this
bright spot appears on the surface is a function of where the
surface is seen from. This type of reflectance is view dependent.
At the microscopic level a specular reflecting surface is
very smooth, and usually these microscopic surface elements are
oriented in the same direction as the surface itself. Specular
reflection is merely the mirror reflection of the light source
in a surface. Thus it should come as no surprise that it is
viewer dependent, since if you stood in front of a mirror and
placed your finger over the refelection of a light, you would
expect that you could reposition your head to look around your
finger and see the light again. An ideal mirror is a purely
specular reflector.
In order to model specular reflection we need to understand
the physics of reflection.