A bloated sci-fi epic if ever there was one, “John Carter” is made watchable by swell effects, passable performances and those little dashes of humor that reassure us that the filmmakers know this is all a lark — no matter what the budget. It begins as a Western, veers into sci-fi, and finally finds its footing as a blend of those, with a dash of sword and sorcery — a Confederate cavalryman slashing and hacking beasties and baddies all over the dusty, dying Red Planet in the years just after America’s Civil War.

Edgar Rice Burroughs, who wrote the “John Carter of Mars” stories, appears as a character here, a young would-be writer (Daryl Sabara of “Spy Kids”) reading the journal of his late uncle (Taylor Kitsch), a swarthy, two-fisted Civil War vet searching for gold out West who stumbled instead into another Civil War — this one a thousand years old and millions of miles away. This one’s taking place on Mars, which is where John Carter wakes up and asks, “Where the hell am I?”

He’s landed in the end game of the Martian Civil War, when two cities — Helium and the mobile city of Zodanga — grinding from place to place on a gigantic crawler — are about to have their final battle. Shape-shifting pan-dimensional beings (led by Mark Strong) have set up Zodanga (led by Dominic West) to deflate Helium (led by Ciaran Hinds).

The armies are clad in gear borrowed from the ancient Romans and flit about in huge, fragile solar-powered flying galleys. There’s the scientist-Princess Dejah (Lynn Collins, who wears the obligatory alien-princess-bare-midriff look well) about to be forcibly married off to Sab Than (West) to bring peace.

Unless Carter, who has swagger — and great leaping abilities on the lower gravity of Mars — intervenes. Of course, first he has to get away from the Tharks, four-armed green nomads who stand 12 feet tall and practice a Spartan brand of warrior culture, musket-armed cavalry who admire nothing so much as a good battle. They brand each other over any offense to the community and practice infanticide.

Kitsch brings a robust manliness to the part of Carter, whom we meet during his brawling / prospecting / Indian-fighting days in the Old West. He’s also got a light touch, which he’ll need in the midst of all this — um — kitsch.

The Tharks hear Carter say he’s from Virginia, and that’s how they name him — “Virginia!” Since they’re ignorant of Jeb Stuart and Robert E. Lee, Carter doesn’t care for that.

The movie has the requisite sword fights and land and sea (air) battles, with the obligatory “Let them to fight in the arena” moment.

“John Carter” is hampered by the staggering amount of exposition that this “introduction of the myth” installment must take care of — races, tribes, names, religions, Martian science about “The Ninth Ray.” Burroughs, who gained his greatest fame inventing “Tarzan of the Apes,” more than gets his due as a writer who envisioned a parallel world in this cinematic blend of hi-tech and retro-costuming, a world with an endless civil war, racism and religious mumbo jumbo.

It’s a state-of-the-digital-art 3-D film with 1930s’ “Flash Gordon” story elements, stuff that probably wasn’t as dated 100 years ago when Burroughs was writing his pulp fiction. A true Disney touch? Playing up the happy, helpful monster “mutt” who takes to Carter and follows him like a puppy.

It’s a popcorn movie, not to be taken any more seriously than “Clash of the Titans” and its ilk. But even by those standards, “John Carter” is a bit of a slog — characters and relationships and conflicts and plot devices to keep track of, none of them worth the brain power you spend sorting them out. A more fun sorting game — trying to identify the voices behind the digitally animated aliens (Thomas Haden Church, Samantha Morton and Willem Dafoe among them).

But Kitsch & Co. make the time pass pleasantly enough. Just try to forget the too-easy comparisons to “Mars Needs Moms” and “Cowboys vs. Aliens” and you’ll be fine.