The blurring of the lines also makes it possible for actors to take credit for the danger.
During a recent interview with "Tonight Show" host Jay Leno, actor Will Smith touted how "real" the stunts were in "Bad Boys II," including an action sequence in which he races a silver Ferrari across a traffic-packed bridge. The film's villains, who have stolen a semi filled with automobiles, begin flinging the cars onto the road.
"In this age of computer-generated images," Smith said proudly, director "Michael Bay went old-school and he shot the stunts for real."
That came as a shock to the staff at Sony Pictures Imageworks, the visual effects powerhouse in Culver City that handled more than 100 digital effects shots for the movie, including the bridge chase scene.
Smith could not be reached for comment. Bay acknowledged that though some stunt work was done traditionally, computers were used to "add dimension that would otherwise have been impossible to achieve."
In the early days of virtual stunts, the technology was so raw that it tended to be limited to the portrayal of animals. The extraordinary dinosaurs of "Jurassic Park," the charming pig in "Babe" and the adorable mouse in "Stuart Little" helped the major studios recognize that computer-generated life forms could be integral, even indispensable, characters in their films.
As the technology developed, virtual humans began cropping up, populating the passenger deck in "Titanic" and the Coliseum stands in "Gladiator." The digital figures were relegated to the work of background extras because they still didn't look believable up close.
For a while, this technological drawback actually helped create new opportunities for stuntmen and stuntwomen.
They could be used as stand-ins for stars who were too busy or too expensive to perform technical stunt work. Instead, a stuntman or stuntwoman would be covered with motion-capture sensors so that each move of an arm or flicker of an eyelid would be stored on a computer and used as a guide for the digital animators to create actual movie footage featuring the stars.
But as the technology became more sophisticated and the animators and visual effects teams gained experience with the emerging tools, the virtual actors were brought closer to the camera lens. And for that reason, a growing number of directors are opting to have the film's actual star, or an actor, move for the computer.
Although stunt people understand how to move their bodies to achieve death-defying acts, few possess the same ability as actors to speak with their bodies and convey emotion through something as simple as a stare.
Such a technique was embraced by "Lord of the Rings" director Peter Jackson, who tapped a Shakespearean stage player named Andy Serkis for the role of Gollum, the wheezing, lisping wretch who stars in two movies in the trilogy.
A stuntman could have walked through the movements of Gollum, said Randall William Cook, director of animation at WETA Digital, the post-production house that handled effects on the "Lord of the Rings" series. "But he's not going to have the charisma of an actor."
Director Ang Lee agrees, and took a similar path on his recent action film "The Hulk."
The visual effects team at Industrial Light & Magic spent months casting various people to act out the role of the angry green monster while wearing a motion-capture suit. Stunt people, body builders, former professional football players -- even ultimate fighters -- slipped into the suit and stalked around a bare stage.
Yet none was able to move in exactly the way that the director, a classically trained Taiwanese actor, wanted. Finally, he began to move his own body as an example. The ILM team began filming.
"By the end, we dumped about 60% to 70% of the footage we had of the stunt people and got Ang into the suit," said Colin Brady, animation director for "The Hulk."
That, of course, is the exception. Digital effects teams continue to rely heavily on stuntmen and stuntwomen to fulfill such roles, and they are not likely to be replaced by computers anytime soon. Ultimately, humans still fill a niche that no computer code can, visual experts say.
"Technology has its limits," said Mark Stetson, visual effects supervisor for "Charlie's Angels: Full Throttle." "Right now, we depend on the stunt coordinator, and they depend on us. We need each other."
That's little solace for many stunt veterans, who say sweeping change is inevitable.
Leonard saw a glimpse of this future in a television commercial that aired during this year's Oscar ceremony. It showed a daredevil motorcyclist roaring off a cliff, and it was done almost entirely digitally.
Leonard found himself admiring the seamless work, until he thought about his 24-year-old-son, Malosi, a former wide receiver for the University of Arizona, who had just broken into the business.
"I said, holy smokes, that's what Malosi's up against."