Visual effects and sound voters are attracted to films that push the envelope of their crafts. But with no obvious, blow-you-away powerhouses like last year’s duo of “The Matrix” and “Star Wars: Episode I — The Phantom Menace,” these categories are wide open this year.Tops on the list are “Gladiator” and “The Perfect Storm.” The digital recreation of ancient Rome offers historical and technical spectacles for Academy voters to chew on, while the stunning waves that thrashed the Andrea Gail made for one of the year’s most memorable images. More cartoony fare often gets its sole Oscar shot in the effects and sound categories, with “Mission: Impossible 2,” “X-Men” “Vertical Limit” and “How the Grinch Stole Christmas” all turning in top-notch work worthy of consideration. But the lightweight subject matter and strength of the more serious “Gladiator” and “Perfect Storm” may work against them this year. More interesting are the less obvious contenders. “The Cell” was inventive visually and aurally but didn’t push the envelope. The digital artistry of “Dinosaur” would be more impressive had we not seen “Jurassic Park.” “The Patriot’s” use of modern action effects and sound is unusual and may come off as inappropriate for a serious historical drama. The fantastic visual of a gorilla turning invisible from the outside in is the only hope “Hollow Man” has for an Oscar nod. And it’s still a mystery whether the Academy and audiences will turn Mandarin-language “Crouching Tiger, Hidden Dragon” into an Oscar powerhouse or an also-ran. Thrillers such as “What Lies Beneath” used sound to great effect, as did the action genre, most notably And don’t count out “Chicken Run.” While its animation status may leave it out of the effects running, sound is a stronger possibility.