The Maelstrom sequence is the film's most daunting innovation. The water is a huge character and the sequence bumps simulation up to a whole new level. All Pirates images © Disney Enterprises Inc. All rights reserved.

After its Oscar-winning performance on Pirates of the Caribbean: Dead Man's Chest, which entailed the groundbreaking Imocap remote performance capture system for Davy Jones and his crusty crew aboard The Flying Dutchman, Industrial Light & Magic had a whole new set of challenges with At World's End.

First, visual effects supervisor John Knoll had a smaller crew to contend with and again was tasked with only five months to complete the work, since this time out his project was the first to finish the season rather than the last. With ILM taking on 750 of the most difficult shots, Roger Guyett was brought aboard to help supervise. He oversaw the shooting of 200 miniature elements and also worked on Captain Jack Sparrow's bizarre hallucination as the wall encrusted member of The Flying Dutchman. "Like Wyvern in Dead Man's Chest, where Jack is inside the wall, we used a similar kind of approach," Guyett suggests, "but the hard part was getting all the texture and doing all the paint work. It is very much a CG character, but Johnny Depp didn't wear the funny gray suit, but he did wear the checkered headband and armbands. We wanted him to still be recognizable." Meanwhile, much more work was farmed out to other vendors this time -- more than 1,000 shots -- under the supervision of Charles Gibson, including Digital Domain, Asylum and The Orphanage. Digital Domain, in fact, worked on 300 shots, including the waterfall sequence, icebergs and the high-speed destruction of an opponent's ship.

This allowed ILM to do the necessary R&D and execution of the film's most daunting innovation: the Maelstrom that envelops both The Black Pearl and The Flying Dutchman during their battle. "The water is a huge character in the movie, taking the technology that we developed over the last few years with simulation but up to a whole new level," Guyett explains. "But to develop the Maelstrom whirlpool, it needed to be a total 3D environment."

In other words, this far exceeded even last year's exemplary work on Poseidon. Indeed, as Knoll concedes, they had to rethink their initial approach. "The assumption at the beginning was, given that the Maelstrom was this very large environment that takes on this whirlpool shape, I thought you could sculpt a funnel shape and then put an ocean surface shader for the sequence. But it was pretty apparent from the first test that we weren't going to get enough visual complexity. This really required full-on computational fluid dynamics. That's a function of resolution, computational power and memory. Even with the biggest 32-gig machines, you couldn't properly convey what was required. What we needed were a few optimization tricks to get maximum amount of detail."

The CG Davy Jones was far less complicated this time around, but still posed some new challenges. Action scenes, including sword fighting, required ways to make the tentacles behave properly.