For the second straight year, the news in Oscar’s visual f/x race isn’t what’s in, but what’s out. When the nominating process began, “The Day After Tomorrow” was the pick of many effects pros. But like 2003’s “Matrix” sequels, it failed to score a mention, possibly due to personality conflicts and a nasty battle over which shops should get Academy credit.That’s not to say that “Day” would have been a shoo-in had it been nommed. Both “Harry Potter and the Prisoner of Azkaban” and “Spider-Man 2” are very popular pics; both did big box office and are finalists for the Visual Effects Society’s single visual effect prize. The third nominee, “I, Robot,” is no slouch either, mixing cutting-edge character work with ambitious CG environments. It’s the only one of the three noms that’s not a sequel, which should work in its favor. “Potter” wowed the Academy of Motion Picture Arts & Sciences’ effects branch with the complexity of its time-turner sequence and the realism of its CGI hippogriff. But the pic’s crowning achievement are the digital dementors, made of fabric that floats in a way never before seen onscreen. “Spider-Man 2,” meanwhile, uses its effects to capture the speed and danger of Spidey’s high-flying battles with Doc Ock. Pic boasts some of the year’s most ambitious digital environment work, including most of its Manhattan streetscapes and an entire elevated-train setting. For sheer volume of effects, though, “I, Robot” takes the prize. It has 1,060 f/x shots — more than half the shots in the film — and it’s the only nominee to offer a major character, robot Sonny, who’s entirely computer generated. “I, Robot” has the advantage of freshness to go with its impressive technology. But some insiders predict that Spidey’s popularity and box office will ultimately make the difference, while the boy wizard’s best-reviewed outing is coming on strong. Harry Potter … Roger Guyett, Tim Burke, John Richardson and Bill George Oscar pedigree: Burke, “Gladiator” (win); George, “Innerspace” (win); Richardson, “Aliens” (win), “Cliffhanger” (nom), “Starship Troopers” (nom) Why it’ll win: The pic was good, and the effects get more impressive every time you look at them. Why it won’t: It’s a sequel and it’s perceived as a kids’ movie, so a lot of Oscar voters may not have bothered to see it in a theater. I, Robot John Nelson, Andrew R. Jones, Erik Nash and Joe Letteri Oscar pedigree: Nelson, “Gladiator” (win); Letteri, “The Lord of the Rings: The Return of the King” (win and Technical Achievement honor) Why it’ll win: It’s the only nominee with a major CG character and its futuristic Chicago is obviously a visual effect — and a good one. Why it won’t: The general membership probably won’t catch some of the subtleties of the f/x work. Spider-Man 2 John Dykstra, Scott Stokdyk, Anthony LaMolinara and John Frazier Oscar pedigree: Dykstra, one win, three noms; Stokdyk, two noms; LaMolinara, one nom; Frazier, five noms Why it’ll win: Pic boasts the biggest gross of the three nominees and combines top-notch effects with a good script. Why it won’t: It’s a sequel, and sequels don’t generally fare well in this category. Also, some of the work’s so good that casual voters may not even realize they’re seeing visual effects.