If you saw Richard Linklater’s Waking Life (2001), you know the drill. He shoots his film with live actors and then computer-paints over them. The process (it takes more than 500 hours to create a mere minute of footage) is called rotoscoping, and he applies it with equal skill to A Scanner Darkly, from a futuristic Philip K. Dick novel well suited to the striking visual dreamscape. Take the scramble suit worn by Keanu Reeves (free of The Lake House, and we’re damn glad of it) as Bob Arctor, a narc working undercover. The suit turns Bob into a walking hologram so that no one can get a fix on his identity, including his pal Freck (Rory Cochrane), who gets the creepy-crawlies when he imagines bugs invading his body. It’s a hallucination of dumbness, despair, desertion and death brought on by the aptly named Substance D, the drug du jour in Bob’s California hood. Also hooked are Luckman and Barris, two hyperarticulate slackers who share Bob’s Anaheim abode. They are played respectively and to the manner born by Woody Harrelson and, in the film’s flashiest and most ferociously entertaining performance, Robert Downey Jr. Dick wrote Scanner in 1977, but the theme of Big Brother surveillance has a this-just-in urgency for the Dubya era. Linklater evokes everything from film noir to the great paranoid thrillers of the 1970s, notably The Parallax View. Bob has gone so far undercover that he’s become worse than the addicts he’s spying on, to the point of bedding Donna (Winona Ryder), a dealer with an endless supply. Linklater’s screenplay is far more convoluted than it needs to be, disorienting audiences when they should be focused on Bob’s psychological meltdown. The breaking point is hit when he becomes the prime suspect in his own sting. The scene in which Barris rats on Bob, not knowing he’s talking to Bob himself — there’s that scramble suit again — encapsulates the moral lines that blur when government fights duplicity with a greater duplicity. Yes, Linklater trips on his ambitions. But this gifted writer-director isn’t out to dull the masses with cinematic opium. Embedded in the visionary headtrip of A Scanner Darkly is a hotly political call to arms.