Despite a long-recognised correlation between actor’s vanity projects and necrosis of the box office, there are still some Hollywood stars prepared to trample on the instincts of writers, directors and casting agents to create monuments to themselves. Bruce Willis was unbound in Hudson Hawk, Schwarzenegger insisted on being basted in his own juice in Last Action Hero, but at least they had the good sense to keep their kids out of it.

Not so the shy and retiring Will Smith, modestly Big Willy to his friends, who at first glance seems to have taken a back seat in M. Night Shyamalan’s After Earth, until you realise that the film’s raison d’être is to promote his 14 year old son Jaden as a sort of genetic tribute to The Fresh Prince: a blue plaque with a face. We soon realise it’s a scheme to replace a star on the wane with a new actor with much the same DNA. Smith will point at Kirk Douglas and Martin Sheen and say, ‘am I no less worthy?’ but launching Smith 2.0 may be a harder sell; this beta version lacks charisma and acting subroutines, which is a pity as he has top billing and a lion’s share of screen time.

Did Jaden want to be an actor or, like his After Earth counterpart, did he feel pressured by Daddy into following in his footsteps, forced to abandon his interest in horticulture? As Kitae Raige, a successful ejaculation from a venerated general in humanity’s ranger core, he’s coping with the guilt of not being able to save his sister from a fear smelling space-beast. Despite being just 9 during the attack, spending the duration hidden in a glass dome thanks to his quick thinking sibling, Smith Senior let it be known via the time honoured parental tradition of being distant and absent, that he didn’t approve of such inaction. Yes, Kitae’s Dad is a cockend but that doesn’t stop this pint-sized copy from wanting to gain his approval by emulating him and becoming a movie star – I mean, a space ranger.

In early scenes, set on humanity’s new alien home world, we’re alerted to the trouble that lies ahead for an audience roped in to this odd power struggle between real life father and son; a psychodrama that’s inexplicably now playing out on our big screen. Will Smith, whose career has been built on charisma and good humour, has challenged his fans to see the intricate matrix of feeling and self-restraint that lies behind his popular persona, playing Cipher as a stiff, emotionless, humourless bore with a flat, monotone voice that’s occasionally inflected by his familiar drawl, but only in those moments where he’s forgotten it’s pretend.

One can understand the confusion. Arguing with your own loinfruit must feel like being at home more often than not. Said child is a space-ball of barely concealed rage (it helps when you have a name to match) that in early scenes, rallying against his ice-cold Dad, resembles a boy who’s been pulled in off the street and asked to screentest because the real auditionee didn’t show up.

Knowing the kid’s going to be front and centre from now on leaves the audience somewhat nervous but fear, we’re reminded, is a choice, so once the Smiths have crashed on Earth, their ship made of thin mesh, plastic sheeting and broom ends, inexplicably succumbing to a meteor shower, it’s better to concentrate on the woodland vistas, CG animals (including the welcome return of Jumanji’s monkeys) and the tech, all of which are of greater interest than junior’s mission to recover an emergency beacon while Will nurses a pair of snapped legs.

Writers Shyamalan and Gary Witta, doing what they can with Big Willy’s story, introduce what they hope will amount to enticing complications – a ticking clock, a dwindling oxygen supply, hostile wildlife and an alien beast on the loose, but director Shyamalan can’t invest the material with any dynamism or tension; he’s as cold and distant as Smith Senior. Consequently all concerned bet the house on Matrix sequel-style platitudinous bullshit, hoping to create the illusion of depth, Honey I Shrunk the Kids holdovers like Jaden battling a giant Eagle, and father and son bickering. It takes more than this for a 14 year old to successfully anchor a would-be blockbuster and long before the end there’s a sense we’re tethered to the bleeding out form of Smith the Elder – drifting into reveries, often on the brink of losing consciousness.

With his box office appeal fading, Will Smith the producer has made some disastrous choices with After Earth. Hiring M. Night Shyamalan is tying one sinking ship to another, and whereas we’re sure he’s proud of Jaden and thinks everything he does is wonderful, humiliating him in front of the world’s movie audiences is likely to lead to their estrangement in the years ahead. In the meantime the project to extend the Smith acting dynasty looks to be dead in the water. “I wanna work with Mom,” says Jaden at the close. It’s not just his on screen Dad he’s talking to.