After the third instalment in the Transformers series, I think I'm a little clearer about the mythos. There's a red car and a yellow car which transform into good robots with blue eyes and wage war with bad robots which are made from black cars and which have red eyes. That, I think, is it. Of course, devotees of the (so-far) trilogy will know that the good robots are called Autobots and the bad ones go by Decepticons, though once the action mayhem begins I doubt that the hardiest fan will be able to say which is which.

Michael Bay, the director, has a few skills, but the ability to convert cranking machines into individualised characters that lay claim to our affections (or our fears) isn't one of them. If you want to see a heavily built automaton attempt a heart-tugging performance, he seems to say, stay home and rent Kindergarten Cop.

But because Steven Spielberg is one of the executive producers, we have at least one scene where a genial Autobot — an extraterrestrial, in a manner of speaking — takes leave of a human before entering a spaceship that will ferry it into the far reaches of outer space. “You will always be my friend,” says the Autobot as strings swell gently in the background, cuing us to feel something. We sit there wondering if the machine is going to cry, and if it does, will it begin to corrode and crumble?

Soon, thankfully, Bay reasserts himself — the moment is not allowed to linger. These machines may not be moving, but at least they move. They shimmy down skyscrapers, vault over freeways, crash-land on the moon, and rip through the skyline of Chicago like a runaway roller coaster propelled by its id. The humans, on the other hand, have little such luck, though at one point, Ken Jeong does take an involuntary dive off his top-floor office.

As with the superhero movies of this summer, a shockingly accomplished cast — Frances McDormand, John Turturro, John Malkovich — attempts to distract us from hollow at the centre, played once again by Shia LaBeouf with all the urgency of a bear in hibernation. The machines may be confusing, but LaBeouf is worse — he's boring.

For the uninitiated, it's hard to say which is worse — staying invested in the human drama woven around this spectacularly underwhelming man, or pretending to care whether the red car with the blue eyes wins over the black car with the red eyes. Boredom is a curious response in a film with so much action, but most of it is put together with the vapid conviction of the modern-day summer blockbuster that a lot of noise and a lot of visual movement is what action entertainment is all about. The aim isn't so much to direct the eye to choreographed movement as drown it in thick sensation.

Depth of field used to be part of the cinematographer's job description — today it comes with the technology. But all the 3-D that money can buy cannot immerse us in anaemic drama. The story begins in the 1960s, with President Kennedy accelerating the moon mission, and ends in the present day, with a besmirched, barely waving American flag feebly announcing its survival after a 9/11-style collapse of sky-scraping architecture. But scratch away this veneer of purpose and it's just never-ending Autobots-versus-Decepticons fights, under the threat of earthly annihilation that animated an earlier film by Bay. This could have been called Armageddonwithit!

And for something with such a mysteriously evocative title — Transformers: Dark of the Moon — where are the images perched at the edge of dream and nightmare? But for a sudden shot of the African wilderness, Bay mires us in the ugly concrete of Anycity, USA. If Hollywood is to be believed, the world, as seen from space, will soon be the Grey Planet, and the question these films raise is this: Is earth really worth saving if seventy per cent of its surface is cement?

Transformers: Dark of the Moon

Genre: Sci-fi / Action-Adventure

Director: Michael Bay

Cast: Shia LaBeouf, Rosie Huntington-Whiteley, Frances McDormand

Storyline: Good robots fight bad robots to save mankind. Or something.

Bottomline: Oh, if you liked the earlier films...