The goal of environment mapping is to render an object as if it were reflective,
so that the colors on its surface are those reflected from its surroundings. In
other words, if you were to look at a perfectly polished, perfectly reflective silver
object in a room, you would see the walls, floor, and other objects in the room
reflected off the object. (A classic example of using environment mapping is the
evil, morphing Cyborg in the film Terminator 2.) The objects whose reflections
you see depend on the position of your eye and on the position and surface angles
of the silver object. Of course, objects are not usually completely reflective, so
the color of the reflection is modulated with the object's actual color for a
realistic look.