Anisotropic is a type of Specular or reflection that simulates the directionality of grooves in a surface and modifies/stretches the Specular in the perpendicular direction. It is very useful when you want to simulate brushed metals, not a metal with a clear, smooth, and polished surface. Imagine the Specular that you see when you look at the data side of a CD or DVD or the way Specular is shaped at the bottom of a pot or pan. You will notice that if you carefully examine the surface, you will see that there is a direction to the grooves in the surface, usually in the way the metal was brushed. When you apply a Specular to this surface, you get a Specular stretched in the perpendicular direction.
This recipe will introduce you to the concept of augmenting your Specular highlights to achieve different types of brushed surfaces. In future recipes, we will look at ways in which we can use the concepts of this recipe to achieve other effects such as stretched...