Recently promoting “For No Good Reason,” the aptly eye-popping new documentary about gonzo artist Ralph Steadman in which he appears, actor Johnny Depp identified the key to his friend’s boundary-pushing genius. “His boldness is shocking,” Depp said simply.

Alas, it has been too long since Depp’s own work seemed bold, shockingly or otherwise. Almost 20 years after delivering peak performances in “Ed Wood” and “Dead Man,” and a decade after the first “Pirates of the Caribbean” film brought him a Davy’s Locker-sized treasure in trade for ingratiating shtick, Depp has hit rock bottom.

In the current sci-fi bomb “Transcendence,” estimated to lose as much as $100 million for Warner Bros., the once effervescent actor, playing a computer researcher who bites the dust in the film’s first half-hour, is reduced to a series of pixilated Skype calls placed from beyond the grave. For a star of Depp’s talent and stature, it’s an embarrassing sight.

But even “Transcendence” can be overcome with the help of video on demand, whereby Depp’s 1990s work for great American filmmakers such as Tim Burton and Jim Jarmusch survives intact.

Nearing its 25th anniversary, the star’s first collaboration with Burton, “Edward Scissorhands” (on iTunes, Vudu and Google Play), continues to cut deep, with Depp tenderly expressing a born outsider’s childlike yearning to fit in. With only John Waters’ “Cry-Baby” to his credit as a big-screen headliner, Depp carved an enormous impression in “Scissorhands,” earning favorable comparison to the likes of Boris Karloff and Charlie Chaplin.

Less appreciated but just as moving is his second film for Burton, “Ed Wood” (iTunes and YouTube), in which Depp miraculously lends heart and soul to the figure of Edward D. Wood Jr., one of the most inept filmmakers the cinema has seen. Manically optimistic despite every conceivable limitation, Depp’s Wood stands as a wonderfully perverse tribute to creative fortitude in the absence of creativity.

Depp’s thrilling devotion to visionary directors hit its peak in the mid-1990s with “Dead Man” (Netflix), in which the actor submerges himself so fully in Jarmusch’s Old West ghost world that he barely seems to exist.

Wandering toward the town of Machine and/or his own grave, Depp’s mild-mannered 1870s accountant is a cowboy-cum-model with shoulder-length hair, oval wire-rims, a top hat, a checkered suit and impossibly glossy lips. Shooting in black-and-white, Jarmusch pulls his camera in so tight at points that Depp comes to resemble a softly out-of-focus actress of the silent period. Indeed, “Dead Man” belongs to all manner of bygone eras — including that of its star’s old-fashioned daring.

Also notable on VOD

“For No Good Reason,” in which Depp bears witness to the creation of Steadman’s still furiously surreal art, starts Friday at Lagoon Cinema. It’s a film that leaves one burning to revisit Depp’s unhinged turn as Steadman’s gonzo co-conspirator Hunter S. Thompson in Terry Gilliam’s “Fear and Loathing in Las Vegas,” repudiated upon its release in squeaky-clean 1998 and now a modern cult classic widely available for rent on demand.

Whether Depp’s hyperactively nutty performance was inspired by some of the same intoxicants that sped Thompson’s prose, “Fear and Loathing” finds the soon-to-be-superstar throwing caution to the wind right from the first scene of his character’s red convertible barreling through the desert as the “drugs began to take hold.”

Totally nailing Thompson’s motormouthed mumble and damn-the-torpedoes approach to journalism, Depp bravely headlined one of the trippiest Hollywood movies ever made. It’s enough to make you wish his work had never sobered up.