The Tribeca Film Festival is going green.“Shrek Forever After,” from DreamWorks Animation and Paramount, will world preem April 21 as the fest’s opening-night film. Directed by Mike Mitchell, the 3D toon is the fourth and final chapter in the blockbuster franchise. Mike Myers, Cameron Diaz, Eddie Murphy and Antonio Banderas return to lead the voice cast. “Shrek Forever” is the second animated 3D film to open a major fest. Last year, Pixar’s “Up” was the opening-night film at Cannes. “We have always sought to open our festival with films that are captivating and strike an emotional chord with moviegoers. ‘Shrek Forever After’ combines the very best storytelling and artistry, while showcasing the wonders of 3D filmmaking,” Tribeca fest co-founder Jane Rosenthal said. “Shrek Forever,” produced by Gina Shay and Teresa Cheng, opens in theaters May 21. In the final chapter, a domesticated Shrek finds himself longing for more adventurous days. Like it or not, his wish comes true when he’s duped into signing a pact with a smooth-talking Rumpelstiltskin. Shrek wakes up in an alternate reality where ogres are hunted and Rumpelstiltskin is king. “It is a great privilege and tribute to our entire cast and crew to have been chosen as this year’s opening night selection,” DreamWorks Animation CEO Jeffrey Katzenberg said. The Tribeca Festival runs April 21-May 2. Full feature film slate will be announced March 10 and March 15.