Originally Posted by Wikipedia
A week into filming, Francis Lawrence felt the infected, who were being portrayed with actors wearing prosthetics, were not convincing. His decision to use computer-generated imagery meant post-production had to be extended and the budget increased. Lawrence explained, "They needed to have an abandon in their performance that you just can’t get out of people in the middle of the night when they’re barefoot. And their metabolisms are really spiked, so they’re constantly hyperventilating, which you can’t really get actors to do for a long time or they pass out."[15] While the infected become vampires in the novel, the film depicts them as "dark seekers" (Anna's term for them)[18] who consume living flesh, with a design inspired by the concept of their adrenal glands being open all the time. The actors remained on set to provide motion capture.[21]
