Filmmaker Brett Morgen promises to paint a more “humanistic portrait” of Kurt Cobain than has ever been rendered in his upcoming HBO documentary that has been eight years in the making.

It took Morgen six years just to sort through the rights issues and gain access to all the personal and artistic material that Cobain left behind after his death in April 1994 at the age of 27. The melodrama of Cobain’s final 48 hours and the self-inflicted gunshot that ended his life will not be featured in “Kurt Cobain: Montage of Heck,” which runs a little over two hours.

The pic, which is nearly finished, is set to bow on HBO next year and will be distribbed in international markets, both as a theatrical release and for TV licensing, by Universal Intl. Pictures Entertainment.

Morgen is known for his 2012 Rolling Stones docu “Crossfire Hurricane” and 2002 study of producer Robert Evans, “The Kid Stays in the Picture.” With “Montage of Heck,” he’s focused on shining a light on Cobain as an artist who worked in many mediums, rock ‘n’ roll being just one of them.

“One thing that will really surprise people in the film is that while we all know about him as a musician and visual artist, we’ll be showing his Super-8 movies, his spoken word poetry and autobiography, his sculptures, his photography and his sound design pieces,” Morgen told Variety. “He worked in just about every medium. These pieces show a world view that no one has seen, and all this material has been sitting in storage boxes for all these years. I’m thrilled we’re going to be able to share it with the world.”

The film came to life with the cooperation of Cobain’s family: his widow, Courtney Love, their daughter, Frances Bean Cobain, and Cobain’s mother, Wendy O’Connor. Love first opened the doors to the Cobain archives to Morgen in 2007, when Frances was still a teenager. By the time he was ready to hunker down on the lensing of the docu, he began working closely with Frances, now a visual artist herself and an exec producer on “Montage of Heck.”

Cobain’s Nirvana bandmates, Dave Grohl and Krist Novoselic, and Universal Music (ruler of the Nirvana catalog) have also given their blessing for use of a wide range of music.

The project fell into place at HBO as Morgen planned his next move on the eve of the “Crossfire Hurricane” premiere. Universal Pictures (which no longer has a corporate affiliation with Universal Music Group) approached Morgen and HBO about an international distribution deal around the same time.

Given the wealth of largely unseen and unheard material, Morgen said there will companion pieces to the movie to showcase the art and musical artifacts.

In all his research, Morgen realized that even the most ardent Nirvana fans have no real sense of who Cobain was, because his interactions with mainstream media were limited during his short time in the spotlight and because he was so guarded in the access that he did grant.

“After going through the archives I could barely recognize the guy in the context of the images of him that have been disseminated by the mainstream media,” Morgen said. “The way Kurt expressed himself in interviews was a pale reflection of who he really was. His warmth, his humor, his creativity was stifled in those interactions.”

Assembling “Montage of Heck” was a challenge for Morgen because it’s the first time he didn’t get to spend an “enormous” amount of time with the subject. For “Kid Stays in the Picture,” Morgen lived with Evans for so long that he joked about becoming “wife No. 9.” But in other ways, the unfettered access to Cobain’s art afforded him great insights. Morgen saw Nirvana perform a few times in the 1990s but never met Cobain.

Cobain’s downward spiral in his final days has been often recounted, which is why the pic stays away from the gory details of his suicide, Morgen said.

The overarching goal of the doc, Morgen said, “is to really challenge the existing mythologies surrounding Kurt and present a very humanistic portrait of one of the great creative artists of our time.”