Every once in a while, a movie comes around that’s so viscerally different from what came before it that the fabric of cinema is permanently altered. To say that future filmmakers were “influenced” by it almost feels like an understatement, as its legacy has less to do with inspiring specific aesthetic innovations than reconceptualizing the way we think about moving images. It’s somewhat ironic that a movie titled “The Texas Chainsaw Massacre” went on to become such a film .

Tobe Hooper’s 1974 slasher masterpiece embraced its lowbrow status with its matter-of-fact title and unapologetic gore, likely seen by many as a cheap attempt to ride shock value into a quick box office gold mine. But as any horror lover will be quick to tell you, that could not be further from the truth. While the film still holds up as a fantastic standalone slasher flick — this writer would argue that it’s better than the original “Halloween,” “Nightmare on Elm Street,” or “Friday the 13th,” for that matter — its most important impact might be the way that it shattered the Overton Window of horror filmmaking, creating a permission structure to show true evil on screen that empowered countless artists to probe the darkest depths of their own minds in search of cinematic scares.

That’s the argument made by “ Chain Reactions ,” Alexandre O. Philippe’s new documentary about the legacy of Hooper’s film. Unlike your typical film history doc, the film wastes little ti.