“Avatar” will seem familiar if you’ve seen “Pocahontas” or “Dances with Wolves,” or any film where an outsider comes to a village and falls in love with the chief’s daughter. You’ll recognize elements from the movies you’ve seen with environmental messages. It also has obvious, un-profound parallels to Iraq and Afghanistan. In short, while writer/director James Cameron is justifiably proud of the groundbreaking special effects employed in “Avatar,” the actual contents of the film — the story, the characters, the dialogue — are disappointingly mediocre. Were it not for the spectacular visuals, this would be a C-grade movie at best.

Oh, but those visuals! Set on a distant moon called Pandora, the film creates, from scratch, a new world with completely convincing plants, animals, and humanoids. The lush jungle scenery is often beautiful to behold. Only George Lucas has invented alien worlds in such fantastic detail, and even his best effects can’t compare to the realism on display here. The computer-generated images interact so seamlessly with the real people that it’s often hard to tell what’s digital and what was actually in front of the camera.

The year is 2154, and an American company is on Pandora to harvest Unobtainium, a valuable energy source found in abundance here. The indigenous people, the Na’vi — thin, blue-skinned, and about 10 feet tall, with catlike facial features — are peaceful jungle-dwellers who worship Eywa, their planet god, and are connected to all of Pandora’s living things. I mean that literally, too: At the end of each Na’vi’s ponytail is a clump of organic fibers that can intertwine with the same fibers on any plant or animal on the planet and exchange information. The Na’vi must hunt in order to eat, but they do it respectfully, and without waste. Naturally, some invading warmongers will need to teach this bunch of blue hippies how we git ‘r done in America!!!

The Na’vi are suspicious of the humans’ intentions, so the company has recruited scientists, doctors, and researchers to help them understand the locals, which really means earning the locals’ trust so they can take their natural resources. The latest improvement is the development of avatars, Na’vi-like bodies, grown in a lab, that humans can control telepathically. You get into what looks like a tanning bed, connect the electrodes, and suddenly you ARE your avatar, free to interact with the natural-born Na’vi like one of their own. Our hero, Jake Sully (Sam Worthington), is a paralyzed Marine who has just arrived on Pandora to take his deceased brother’s spot in the avatar program. The added bonus for Jake is that, through his avatar, he can walk again.

Under the direction of a gruff scientist named Grace Augustine (Sigourney Weaver), these avatars have made some inroads with the Na’vi and have learned a lot about their planet’s biology, but they still haven’t gotten them to hand over their Unobtainium deposits. That’s why we have guns. The company seeking profits here, represented by a slimy corporate type named Selfridge (Giovanni Ribisi), has brought in military contractors, led by Col. Quaritch (Stephen Lang), a stereotypical jarhead who’s tired of diplomacy and thinks we ought to just attack. Kill ’em all and let Eywa sort ’em out, that’s his policy. Selfridge is only mildly resistant to this course of action, having no sympathy whatsoever for the Na’vi. (“Fly-bitten savages,” he calls them.) He probably expects them to move off “his” land and open some casinos. Still, he’ll hold off on the heavy artillery for now if Grace’s avatars can make a peaceful negotiation.

As an avatar, Jake meets Neytiri (Zoe Saldana), who is apparently beautiful, though to be honest all the Na’vi look alike to me. (Please don’t call me a racist!) And why he would be physically attracted to a 10-foot-tall blue woman anyway, I don’t know. The point is, they meet, and she knows he’s a human in an avatar body — how much the Na’vi know about that whole system is unclear, but she calls him a “dreamwalker” — and she’s the daughter of her tribe’s leader. Jake earns her trust and is gradually introduced to the tribe. Predictably, he goes native and comes to doubt his original mission of learning more about the Na’vi so that Col. Quaritch will know where to invade.

Unfortunately, there are a lot of predictable things here — the story has no surprises at all. Once the basics have been established and the story starts moving, you could stop the film at any point, guess what’s going to happen next, and be right almost every time. Take it out of its otherworldly setting, replace the aliens with humans, and you’ve got a plain, generic eco-fable.

The dialogue is no help, either. It’s mostly functional, with little wit or flavor, nothing but a series of cliches pulled from war movies. One character gets shot and says, grimly, “This is gonna ruin my whole day.” Col. Quaritch comes across as a parody of over-the-top military figures, telling his men just before an attack, “All right, ladies! Let’s bring the pain!” At one point he actually uses the term “shock and awe.” He and most of the other characters (including Michelle Rodriguez as a tough Marine pilot), though seen in 3D, are quite one-dimensional, not just in their derivative dialogue but in their personalities and motivations.

The same is true of Jake and Neytiri, the lead characters. We get very little sense of who they are other than star-crossed lovers. Are they playful? Stubborn? Clever? Resourceful? Shy? Curious? What? They are nothing — they have the standard traits that heroes and heroines in action movies usually have, i.e., generic bravery and vague nobility. And I’m sorry, but if I’m going to spend over 2 1/2 hours with a group of characters, I’d like those characters to be, you know, interesting. Save the stock characters for your B-list projects, not your massive, 162-minute ones.

But yeah, the film is pretty cool to look at, and the pace picks up considerably in the last half-hour, when the heavy action begins. The story remains uncompelling, but at least the battles are spectacular, perhaps more so because of the fully immersive 3D. A movie this big ought to offer more than just special effects, though, no matter how fantastic they are. A film that raised the bar technologically and also told a great story with memorable characters? Now that would be a game-changer.

B- (2 hrs., 42 min.; PG-13, moderate profanity, a lot of action violence, a bit of mild sexuality.)