The 2010 remake of Ray Harryhausen’s 1981 “Clash of the Titans”—which wasn’t one of the master animator’s best to begin with—coasted to success on the then-novelty of the 3D format, into which it had been rather poorly converted before release. This sequel is in 3D, too—the real thing this time, not an afterthought—but the format has become so ubiquitous that it’s no longer a particular selling point. “Wrath of the Titans” has to get by on its merits, and there are very few of those to be found in this clunky, muddled mishmash of Greek mythology, which is mostly notable for loudness, splashy but unimpressive effects and the sight of some decent actors slumming it up. One of them, Liam Neeson, sagely intones “There’s a catastrophe coming” early on, and the line turns out to be strangely prescient.

The plot is a very simple one. The Titans, led by Kronos, remain imprisoned in Tartarus as a result of the ancient rebellion of his sons Zeus (Liam Neeson), Poseidon (Danny Huston) and Hades (Ralph Fiennes). But the power of the gods is waning due to decreased human reverence for them—the premise of “Clash”—and Zeus must turn for help to his half-human son Perseus (Sam Worthington), who showed his mettle by defeating the Kraken and saving Argos and its queen Andromeda (Rosamund Pike, replacing Alexa Davalos). But the widowed Perseus declines to get involved, preferring to live as a simple human fisherman and raise his son Helios (John Bell).

Matters change, however, when Hades turns against his two brothers, and together with Zeus’ son Ares (Edgar Ramirez), the god of war, plot to empower Kronos to escape the confines of Tartarus by draining Zeus of his power. If the Titans are released, they will destroy humanity and ravage the earth. So Perseus is compelled to try to enter Tartarus, liberate Zeus, and by joining together the weapons for the three brothers forged by the exiled Hephaestus (Bill Nighy), overcome Hades and Ares, defeat Kronos and save humanity. In doing so he will join forces with Andromeda and the obligatory bad-boy, Poseidon’s half-human son Agenor (Toby Kebbell).

“Wrath” is filled with episodes that allow the effects team to take over—an attack on Perseus’ village by a winged, fire-breathing monster, Perseus’ reunion with the winged horse Pegasus, the team’s encounter with the some initially unfriendly Cyclopes, the descent into Tartarus via a labyrinth of earth and rock, a battle with the Minotaur, and of course the final confrontation with the escaped Kronos, a huge undulating mass of magnum and mud that looks like a fiery version of the Sandman from “Spider-Man 3.” And then there are fights, loads of them, with Perseus facing off repeatedly against Ares and faring poorly most of the time. Good thing he’s a demigod who can survive all the pummeling.

None of it means anything emotionally, of course. The script tries desperately to develop a father-son theme focused on Perseus’ love for his boy and his reconciliation with his father. (This is pretty much a macho enterprise, with Andromeda a cursory nod toward the feminine as warrior princess.) But it never takes. And the writers add occasional moments of juvenile humor in a hopeless effort to lighten the mood.

But “Wrath of the Titans” remains a dour, dank attempt at a mythological spectacle, a quintessential B-movie that’s not elevated by all the florid CGI—less murky than in the previous installment but still mediocre—and the 3D addenda, mostly consisting of rocks, volcanic ash, and occasionally bodies flying toward the audience, which seem purely pro forma. The performances are just serviceable, with Worthington wooden, Pike mere eye candy and Kebbell trying far too hard to seem the charming rogue. Among the gods Neeson sleepily mouths his hackneyed lines with stentorian oomph, while Fiennes underplays, perhaps trying to make up for his overemphatic Voldemort. (Huston has little more than a cameo, and seems happy to hide beneath a massive beard.) Garcia, as Ares, and Nighy, as Hephaestus, balance things out by hamming it up mercilessly.

In the end what’s lacking in the movie, though, is the sense of fun that Harryhausen and his cohorts brought to their films, even the lesser ones like “Clash of the Titans.” You come out of it feeling drained and depressed rather than exhilarated.