Let’s get it out of the way: Avatar is undoubtedly the most spectacular science fiction epic you’ll have seen. It sets a new benchmark in gee-whiz effects based lunacy, and will remain the touchstone for this kind of thing for some while.

All very well, but what’s it about? There are two answers to that question. One is to say that it’s to do with the interaction of humans with an alien race on the planet of Pandora, aliens who unfortunately for them live on top of a massively desirable mineral that Earth can’t get enough of, and the consequences of that conflict.

More interestingly, Avatar is basically what would happen if you took a probe into James Cameron’s brain and put what you found in a petri dish to create a very particular culture. Only, for petri dish read ‘gazillions worth of software and hardware’. But the point remains: what we’re seeing here is much of what makes James Cameron tick.

Rewind 35 years, more maybe. A young Jimmy Cameron sits reading the Whole Earth Catalog and listening to that Yes album with floating islands on the cover, tv on but sound turned down, images of Vietnam playing onscreen. He’s been smoking weed, and the resulting high has taken him to a kaleidoscopic vision of a story that mixes Roger Dean’s airbrushed psychedelia with eco-fable and a dose of anti-war activism. Damn, thinks Jimmy, coming back to Earth as the joint drops a hot rock on his cheesecloth shirt, I’d give anything to see a film with all that crazy shit kicking off.

And so it came to pass that Jimmy Cameron grew up to become the celebrated filmmaker James Cameron. Along the way he made two sequels that redefined their franchises, Alien and Terminator, before creating the humungous hit that was Titanic. And now he’s written and directed Avatar: can it really be bigger than what he’s done before?

Avatar is enormous, in every possible way. And, most of the time, it justifies the ridiculous attention to detail that went into making it. A bravura opening scene showcases the technology that Cameron’s people have come up with, as space marines emerge from stasis in zero gravity. They swoop down to the surface of Pandora, where humans have established a mining facility: it’s here, in a relatively subtle bit of visual storytelling, that we realise we’re not welcome on the planet when arrows are seen protruding from a vehicle’s bulbous tyres.

The protagonist — played by Sam Worthington — is a marine in a wheelchair, disregarded by his colleagues but immensely valuable to the science team since he shares the genotype of his deceased twin brother, trained up to pilot a human clone of one of the resident aliens via a high-tech interface. Some of the scientists resent the soldier in their midst, but without that background Sam wouldn’t have the survival skills to get by on the deadly planet.

Sam does more than survive — he thrives, taken under the wing of a clan chief’s daughter, who mentors him to become one of her people, and ultimately becomes his lover. That story arc is played out against another one, as humans on Pandora increase the aggression of their campaign against the natives, and destroy the massive sacred tree they live in.

Human aggression and arrogance backfires: unable to comprehend that the natives have a sophisticated culture biologically linked to the planet’s ecosystem, the military are ill-prepared for the way that Pandora fights back. And because this is what we want to see, the aliens succeed in turning the tide and defeat the humans, in a titanic battle amid the very same floating islands that young Jimmy tripped out to back when he was listening to Yes.

This is mythic, bombastic stuff, and it’s very good at realising that vision on a technical and story level. It would be churlish to dismiss the prowess with which Avatar delivers its particular goods, and I have no desire to: if you relish cinema that’s as grandiose as Wagner working with Jim Steinman, you’ll find plenty to enjoy here. If not, do yourself a favour and stay away: some of us want to wave our cigarette lighters in the air.