There's nothing respectable at all about beating up on a 14-year-old in print, and it is the inalienable right of Jaden Smith to be 14 years old, something that most of us were at some point. But this leaves us at something of an impasse, because Smith is the chief problem with After Earth, a movie that is unrelievedly terrible, but might very well have been simply mediocre with any other lead performance. It being impossible to really discuss everything that is horrible with the film without saying some very nasty things about the performer, and it being impossible to say nasty things about the performer without feeling like an asshole - even if one of the most privileged, wealthy adolescents in the history of mankind can probably stand up just fine to a few bullying bloggers - I've run smack into a wall.

After Earth, as ginned up by God knows how many script doctors from a story originating with the film's producer and co-star Will Smith, takes place an ill-expressed number of hundreds of years in the future, a millennium after humanity was forced to abandon our home planet by a thing, probably to do with environmental catastrophe. Exposition isn't a strong suit here, with the movie plunging us right into a staccato-edited montage of a spaceship crashing and a survivor being flung out into a field as Jaden monotonously reads some voiceover that sets the scene in the murkiest possible way: there are evil fear-smelling alien monsters called Ursa that the assembly of the opening suggests were part of the reason humanity fled, but then it's also the case that the Ursa have only been a problem for a couple of generations, and whatever, it doesn't matter. Earth is a ghastly wasteland, humanity lives on a far off-planet, and Kitai Raige (Smith fils) is the son and only surviving child of the war hero Cypher Raige (Smith père), whose daughter Senshi (Zoë Isabella Kravitz, seen as an inspiring memory) was killed by the Ursa about five years prior. The relationship between the elder and younger Raiges has been clipped and official ever since then, with the boy attempting to join the Ranger Corps commanded by his father in an effort to prove his independent masculinity and also win his father's love.

He fails to do any of these things, but his mother Faia (Sophie Okonedo, spectacularly wasted by a two-scene role in the first movie she's appeared in since 2008) leans upon her husband to take Kitai with on a routine mission, Cypher's last prior to retirement. Now, routine missions that happen right before retiring can only go spectacularly wrong, which is how the Kaiges end up being the only survivors of a crash-landing on a planet that proves to be the long-abandoned Earth, having been damaged in a freak asteroid storm. There is absolutely no part of this that suggests that the screenwriters - of whom only director M. Night Shyamalan and Gary Whitta receive credit - understand how big space is, even granting the need to tell a pulpy B-movie story. There's no reason for asteroids to be that close to a planet, or for Earth's solar system to be directly between the new human homeworld and their destination, or for space travel across the galaxy to take, seemingly a day trip, and no reason that the movie requires any of these things to be true in order to tell exactly the same story. But let's not start marking up the script with a red pen, or we'll never get to the movie's myriad other failings. Anyway, the remaining bulk of the film is a survival story: Cypher has been terribly wounded in the crash, and he needs Kitai to trek 100 kilometers to the other piece of their broken spaceship to launch a distress beacon. The two Raiges will be linked by a wrist communicator that will broadcast images of Kitai's trek, and which Cypher stresses must absolutely not be lost or damaged, to make sure we understand that it will be later on.

When the film gets to this stage of the plot, it honestly does improve enormously: the opening act is so dismal and leaden in its establishment of threadbare emotional stakes, crudely and confusingly building its world, and showcasing the very worst acting that either Smith will indulge in for the rest of the movie, so "improvement" is a relative concept. Rising up to the level of Shyamalan's last film, the rancid The Last Airbender would have qualified as "improving". But, in fact, After Earth ends becoming even better still than that, for it not only stops requiring Jaden Smith to express complicated emotions, it also allows Shyamalan to do just about the last thing that he's still capable of, putting the camera up in places to make a big, sprawling world of amazing sights seem indefinably menacing; it's probably his best film since The Village, in fact, which would be a really mean thing to say about anybody who wasn't the auteur behind Lady in the Water.

True, After Earth is never less than bone-stupid, even at is most visually inspired: most of Kitai's trek is something like Avatar on a budget, tromping through the strangeness of post-apocalyptic Earth and finding a mesmerising array of exotic species, a mere thousand years in the future; looking at the rate that speciation has happened in the last millennium, it seems rather dubious that entire new big cat and giant bird species would emerge so soon, but let's blame ecological tampering. It's even less likely that the continents would be as dramatically different as they're suggested to be during the end credits, but let's blame... nukes. The point being, After Earth fails completely to earn its title, presenting a fantasy world of Earth that only introduces logical objections that wouldn't arise if it was just a random alien world, while failing to present any post-apocalyptic ruined cities or signs of human habitation that would justify the Terran setting in the first place. Certainly, the only decent monster design is the Ursa that naturally shows up just in time for the climax, instead of providing a constant threat that the movie could use to build tension.

The empty spectacle here is thus even emptier than usual, though poor Shyamalan dodges most of the responsibility, I think: he leadenly and mechanically shifts out from one survivalist setpiece to the next, with little ingenuity but just enough skill that you can squint and see the remains of a solid popcorn director reduced to playing a good little director-for-hire. The chief failings are conceptual, and can be blamed mostly on Will Smith; and in charcterisation, and can also be blamed on Smith, who allegedly took the lead on directing his son, and is thus probably the reason for the awful Carib-Pacific accents that everybody has in the future! even as they are all still members of various modern-day ethnic races, and for the hellishly earnest, dusty, dead performances given by both himself and his son. They are miserable dour people, these Raiges (and seriously, Cypher Raige? Sounds like the villain in an '80s Van Damme movie), and though the film's overt plot is about overcoming your fear, Jaden doesn't have nearly the range to imply that fear is a thing he ever feels to begin with. The result is a bland adventure film spoiled on dreadful, unlikable characters, in a movie not nearly fun-bad enough to mock, or to get any sort of accidental pleasure out of whatsoever. It's a vanity project of the most pinched and mirthless sort, and very little can be imagined that's duller than that.