Will Smith in I Am Legend Courtesy of Warner Bros.

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Relaxed and upbeat — naturally — Will Smith takes a break on an interior set for his new movie I Am Legend. The set is constructed in a hangar-like space in a New York State Armory building in Brooklyn, and the actor, wearing a vest and tracksuit pants, has interrupted his lunchtime training session to provide some insight into the film.

"I love that I'm training while everybody else is eating," Smith quips. Parked outside for the two-time Oscar-nominated actor is an enormous, gleaming, double-storied black trailer with a fully equipped gym.

Smith must keep buff to play scientist Robert Neville in I Am Legend, in which Neville battles zombie-like plague victims whose condition deteriorates into a kind of vampirism. Understandably, a typical day in Neville's life is a far departure from Smith's relatively pampered workaday existence. The actor's description highlights the character's solitude: "The day is really structured. My character has a PTSD, post-traumatic stress disorder, so in post-traumatic stress disorder everything has to be really organized for this character or things start bugging out. So his day is very organized. I have to sit up all night. So pretty much from sundown to sunset, I sit awake and I watch my monitors. I have cameras all around the house to see if the dark seekers were to make their way. At sunrise, I get a couple of hours sleep and go into my lab — my character is trying to work on a cure to reverse the KV virus. Then after a few hours in the lab, I go and pillage. I'll go through people's apartments to find food, to find weapons, to find whatever I can for storage. Then at noon I sit. I'll wait at the South Street Seaport.

"I've made a message that I transmit on all AM frequencies: 'My name is Robert Neville. I'm a survivor. I can provide food. I can provide shelter. I can provide security. Please meet me at noon when the sun is highest in the sky.' So I sit and I'll wait. I do work. It's kind of just me and my dog."

The description also emphasizes the amount of time that Smith occupies the screen completely alone. Though he will not be in every shot, he will be in every scene.

"It is absolutely terrifying," he says of the pressure of propelling the action while acting alone. "The drama is about conflict. So when you're by yourself, it's kind of difficult to find conflict, and as an actor that's what you're looking for. What is the character's need and what is the conflict with that? So when you go scene by scene by yourself, it's difficult to find that."