Filming a movie like Avatar is an enormous project for the graphics teams. The reason the Avatar's look so life like is based on the technology they were able to use. If you look closely, there are a bunch of tiny green dots on the woman's face in the top picture. These dots tracked her facial expressions and transferred them to the movie screen. The suits they wore while acting it out also served for the same purpose. Then the graphics filled that in creating the blue creatures that we cherish on the screen.