The last recipe demonstrated how to create a color map that can be accurately UV-mapped around a complex model of a human head. We could just take that color map and apply it in a simple material. However, in real life, the human face has many more surface irregularities than just color. If you examine your own face, you will see that veins, hair sockets, and smile line creases add detail to show what kind of a person you are. Likewise, your skin will reflect light more on those areas of your face that are wetter than others. This natural sweat will vary across the face, not only explaining the environment or temperature, but also what you may have been doing like running or resting. Adding maps to control these material attributes will help add detail to convince the viewer they are looking at human skin rather than plastic painted as skin.
Creating bump, specular, and shading maps is not as difficult as it sounds. We can use...