Unnecessary but never uninteresting, Texas Chainsaw at least tries to sharpen the long-dulled blade for this, the seventh appearance of Leatherface — wielder of power tools, wearer of skin masks and butcherer of the curvaceous and chiseled.

After this and 2010’s so-so heist film Takers, director John Luessenhop is an acolyte of the inoffensively unremarkable genre picture. Here, he breaks up expected carnage with just the right amount of misdirection and distraction — an unexpected detour to a carnival, suspense that’s sparked by light, clinking sound effects instead of loud clunks, leading lady Alexandra Daddario’s supernaturally hypnotic midriff.

When four-fifths of the pretty people are dead by the halfway mark, that’s a lot of movie left. Does the remainder predictably borrow from A Nightmare on Elm Street and later Halloween installments? Sure. But unlike most “Chainsaw” sequels and prequels, at least it’s not a painful slog to the finish.

The best, and worst, aspect of Texas Chainsaw is its reclamation of the series’ timeline after 39 back-and-forth years — junking films two through six and picking up hours after the conclusion of Tobe Hooper’s zeitgeist-capturing original.

It’s great because this installment is no longer tethered to a 2006 prequel’s outhouse-Freud BS about Leatherface’s lousy childhood. It’s bad because it incongruously places the original’s events in the era of Clinton, not Nixon. Then again, if Daddario’s character is 40, she has the best ab workout DVD ever made.

The prologue presents snippets of the original (re-rendered in 3D), cameos pointless for all but franchise faithful, and, in new footage, the murderous Sawyer family’s farmhouse shot and torched by redneck vigilantes a la Ruby Ridge. The only seeming survivor is a newborn baby plucked from the aftermath and parented by two hateful hayseeds who leave town. But not for nothing does the camera linger.

With a wink, the film leaps forward in time, where Heather (Daddario) is a meat-counter clerk — smuggling home animal bones with which to mount decrepit works of art at the apartment she shares with kickboxing boyfriend Ryan (rapper-turned-actor Tremaine “Trey Songz” Neverson).

Neverson’s most meaningful contribution is to the soundtrack. He cops Chris “Ludacris” Bridges’ preferred billing but none of his presence. Plus, the movie deprives us of a scene in which Ryan’s leg is severed mid-roundhouse that it so mercilessly teases early on. More intriguing: As Songz’s song goes, Ryan is more interested in the ladies and the drinks than he initially lets on.

The couple is headed to New Orleans for Halloween with vixen / bestie Nikki (Tania Raymonde, best known as Alex from Lost) and Nikki’s crepe-cooking new squeeze, Kenny (Keram Malicki-Sanchez), in tow. But when Heather inherits an estate from a grandmother she never knew, they detour to tiny Newt, Texas — where the pit-pooling sweaty aesthetic is on point and the usual dumb-dumb domino effect sets events in motion.

Rule No. 1 of Home Ownership: Don’t leave a handsome hitchhiker (Shaun Sipos) alone in your new house to pilfer silver and release a long-locked-away killer who’s lived on turkey legs and lemonade for 20 years. Rule No. 2 of Home Ownership: If your inherited home comes with a set of rules, read them promptly as instructed.

The trashy 3D, rarely worth the upcharge, is more invasive than inventive — often augmenting cut-rate computer-generated spatter. (The best digital effect is the deletion of the “C” from the sign of a Clark gas station — a missed product-placement opportunity to be known as the place for snacks before slaughter.) But Luessenhop balances the blood and bombast with several icy compositions.

One shot strikingly overlays Daddario’s face atop a wide- and crazy-eyed portrait of her birth mother. And where most would show a crashing van’s glass and metal from every angle, Luessenhop opts for an iconic, distantly wide shot indicative of the helplessness inherent to the horror genre. At least he brings a bit of artistry into this abattoir of removed faces, blasted brains, sliced tendons and bisected bohunks.

The story often hangs looser than Daddario’s blouses from her bosomy frame. But as it sufficiently and sinisterly outs small-town skeletons we know are lurking, it injects bits of cracker comedy as amusing as they are grisly and courteously keeps Leatherface’s psychological profile low and less obvious than a Stihl to the stomach.

In such slabs of beef, there’s always going to be gristle. At least Luessenhop and company cut around it and sear in enough seasoning to serve something that, as cheapie-roadside cinematic meals go, is surprisingly digestible.