As the final chapter in the “Shrek” series is prepped for its bow in theaters, franchise director-writer-producer Andrew Adamson is embarking on his next adventure: big-budget fantasy “Fountain City.”

L.A.-based Lightstream Pictures has preemptively picked up the live-action pic, which it will co-finance. Budget is projected at more than $100 million; storyline is being kept under wraps.

Adamson and scribe Joby Harold sold the fantasy-adventure to Lightstream based on Harold’s original idea. Harold is penning the script, which Adamson will direct.

Producers of “Fountain City” are Adamson, Aron Warner and Lightstream. Tory Tunnell is also a producer; Jeff Fierson will co-produce. Harold will exec produce.

Garrett Kelleher, an Irish entrepreneur, founded Lightstream Pictures in 2007 with Lawrence Inglee and Paul Currie. Inglee is a producer who worked for years at the Mark Gordon Co. He began his career at Imagine Entertainment.

Currie is an Australian filmmaker who will direct 3-D animated feature “The Fourth Wise Man” for the company.

Lightstream was launched with the goal of producing and financing tentpole and prestige feature films. It includes an animation/visual effects studio, Lightstream Animation, based in Petaluma, Calif.

Adamson directed the first “Shrek” film and wrote and helmed “Shrek 2.” He left the franchise to helm Disney’s “The Chronicles of Narnia: The Lion, the Witch and the Wardrobe,” but exec produced both “Shrek the Third” and the upcoming “Shrek Forever After.”

Adamson also directed the second “Narnia” pic before Walden Media took the franchise from the Mouse House to 20th Century Fox.

Harold’s credits include adapting Frank Miller’s D.C. Comics series “Ronin” for Warner Bros. He also wrote and directed “Awake” for MGM.

Adamson is repped by UTA, which also is helping to line up additional financing; Harold is repped by CAA.