Director Francis Lawrence’s I Am Legend is the third official version of Richard Matheson’s seminal 1955 novel about a lone man trying to survive after a virus turns the rest of humanity into some sort of zombie/vampire hybrid and the only one to actually bear its name. First (and still beloved by many) was the 1963 Vincent Price vehicle The Last Man on Earth. Then there was 1971’s The Omega Man, directed by Boris Sagal, with a much bigger budget and Charlton Heston to boot.

IMDb lists two others that don’t credit Matheson’s book: Soy leyenda (1967), which does keep the name, albeit in Spanish; and the amusingly entitled I Am Omega, which went straight to video only a few weeks ago.

So what does the new Will Smith version bring to the table, besides a budget somewhere between 100 and 1,000 times greater than the 1963 version?

I Am Legend opens with a brief, amusing prologue — no more than a minute or two — in which the kindly but ominously-named Dr. Crippen (an unbilled Emma Thompson) explains in a TV interview the wonderful new virus she has developed to wipe out cancer. Of course, these technologies sometimes backfire: The next thing we know, it is three years later, and we see a montage of Manhattan as a ghost town, with a sole car speeding through the streets.

Driving that car, of course, is our hero, Robert Neville (Will Smith), accompanied by his faithful dog, Sam. For no clear reason, Neville is one of the few to be immune to the virus, which is convenient, given that he used to be the Army’s chief virologist for the area. He broadcasts a radio message every day but suspects he is the last uninfected human alive.

The effect of the virus is to make people creatures of pure aggression. Like vampires, they can’t stand sunlight, so roving bands only come out at night, running like track stars, ready to attack anyone, infected or not, preying upon animals and weaker humans.

He spends the days rounding up supplies and generally enjoying the upside of having Manhattan to himself. (The Army destroyed all access routes to the island hoping the viral outbreak there could be contained.) But at sundown he retreats to his amazingly well-defended house, closes the giant metal shutters over the windows and doors, and returns to his even better fortified basement lab, where he is still trying to find some way to reverse the effects of the virus.

Just about now, you may start wondering how he has kept the place running. He uses a lot of high-tech equipment, including a bunch of computers, all requiring electricity, which he has in copious supply. (In the 1963 version, we see Price feeding his gasoline-driven generator; if Smith has something similar, it went right past me.) And how did he armor-plate his house after the plague started? Did he haul all those huge steel plates into position himself?

Ah, well, never mind. Those are just little details that could easily slip right by you, because — and this is the most important thing — you’re too busy worrying about Smith to notice. As always, he immediately invites identification. He is a good actor, but he has that other, rarer star thing that makes us like him within seconds after he appears on screen.

Director Lawrence got his start doing music videos, which was pretty obvious from his silly feature debut, Constantine. He fares substantially better here. Much of his success comes from sheer button-pushing, with threatening figures suddenly leaping into frame from behind the camera. But much of what’s effective derives from Smith’s performance and from the carefully built emotional substructure.

The “zombies” themselves, with their ferocity and speed, might have seemed really fresh if this project hadn’t been delayed since the ’90s, when it was supposed to be a Schwarzenegger vehicle. In the interim, 28 Days Later was released, with a similar backstory and non-Romero-style “zombies.”

Nonetheless, I Am Legend does its job very well: We jump, we cringe, we even weep. Sometimes it goes just a little beyond the predictable as well. There is a funny scene not far from the end that shows how years without human contact can make you squirrelly in ways that aren’t obvious until other people are around. It points up the movie’s thematic resemblances to Cast Away, which remains the gold standard on the subject.