One franchise is apparently insufficient for a star as awesome as Vin Diesel, so in addition to the “Fast and Furious” series he continues to treat us to episodes in the history of antihero Richard B. Riddick, whom he and writer-director David Twohy introduced in “Pitch Black” and then brought back in the larger but lumbering “The Riddick Chronicles.” Taken together, the trilogy might make you wish he had decided to continue with “The Pacifier” instead.

Actually, “Riddick”—the very direct title given to this third installment—could pass muster as a brainless action flick if its throwaway laugh lines weren’t so terrible and it weren’t unconscionably overlong at a full two hours. Certainly it won’t get any points for originality. Following the pattern of “Pitch Black,” which really wasn’t much more than a bargain-basement “Aliens” clone, it situates the brawny protagonist—after a perfunctory introduction that slides over the outcome of the second picture—on a planet populated only by hostile creatures (big, ravenous canines and huge scorpion snakes that ooze out of muddy ponds). But when he sets off an emergency beacon, it immediately brings two shiploads of well-armed mercenaries, all looking forward to bagging the universe’s most-wanted criminal and taking him back to civilization dead or alive for a substantial reward (doubled, in fact, if he’s dead).

The remainder of the movie consists of cat-and-mouse games—between the humans and the native beasts, between the two groups of mercenaries, and of course between Riddick and the mercs, as they’re called—before those who’ve survived the initial attacks of nasty creatures must band together to get the ships back in the air and themselves out of harm’s way. Much of what passes for plot centers on Riddick’s manipulation of the situation to insure that he’ll not only come out of it alive but go free. But he’s also given the illusion of depth in a half-hour sequence before the mercenaries arrive, during which he frees himself from the rubble in which he’s buried, resets his own broken leg, confronts the snake monsters and the canines (even adopting one of their pups, which becomes his pet), and generally shows us what it really means to be macho.

Part of the problem with “Riddick” is that as played monochromatically by Diesel, the title character is just a smug thug with a basso profundo voice and ultra-sensitive eyes that glow when they see in the dark. His prophetic pronouncements—usually threats against somebody or other—are supposed to be darkly humorous, but they come across instead as silly; there have been glum action heroes before, but Ruddick’s presumed charisma is an acquired taste it’s definitely easy to resist. The rest of the ensemble isn’t any more interesting. One group of mercenaries is led by Santana (over-the-top Jordi Malla), a wild, reckless, and as it turns out thoroughly inept loudmouth who suffers an end Riddick predicts well in advance (and his fans in the audience will cheer). The other is commanded by Johns (bland Matt Nable), who has a very personal interest in confronting Riddick that those who’ve seen previous installments in the series will especially appreciate.

Otherwise the mercenary crews are a bunch of largely pro-forma figures. The only ones that stand out from the pack of rough, stubble-wearing, burly types are the sole female, sharpshooter Dahl (Katee Sackhoff), who kicks butt with the best of them while managing to look positively seductive in her tight leather outfit, and Luna (Nolan Gerard Funk), the nervous rookie who spouts prayers at every tense moment (though what such a wet-behind-the-ears kid is doing among a pack of cutthroats is never explained). It must be admitted, though, that as Diaz former pro wrestler Dave Bautista does outdo the others in bulk alone, and the inevitable face-off between him and Diesel challenges the brontosaurus-tyrannosaurus rex battle in “The Lost World” for grandiosity.

Twohy manages some sudden shocks (helped by Tracy Adams’ editing and Graeme Revell’s big-bang score), and by and large proves more than adequate directing the action scenes, though his handling of the dialogue-driven interludes is pretty ham-fisted, and he and Diesel have a hard time wringing any emotion from an “Old Yeller” moment tossed into the mix. The visual effects are adequate on what would appear to be a pretty tight budget, though neither the vast landscapes nor the alien creatures are state-of-the-art. The fact that a 3D conversion was eschewed is a point in the movie’s favor.

By going back to basics after the goofy excesses of “Chronicles,” this installment will prove popular with fans of brainless action movies and/or the massively inexpressive Diesel. But there’s nothing special about “Riddick,” which is no more than a mostly competent but utterly mediocre exercise in outer-space mayhem.