The Letterman Digital Arts Center, on the green and lush grounds of San Francisco's Presidio, looks like just one more office complex among the Bay Area's many high-tech companies -- until you notice the statue of Yoda atop the fountain out front. In late October, Cinematical and other websites and newspapers were invited to the Letterman Center to get a glimpse into the making of Pirates of the Caribbean: At World's End thanks to one of the center's tenants, Industrial Light and Magic -- the special effects powerhouse created by George Lucas for the Star Wars films that's come to dominate the field with their excellence in the pursuit of movie making wonder. In the gallery below, you'll find the Disney-provided photos from that day giving you a glimpse of the special material we were shown about Pirates III -- as well as Cinematical's own snapshots of the wonderful, weird and bizarre souvenirs of special effects triumphs from the past that line the walls of the center.

As for the special effects secrets behind Pirates of the Caribbean: At World's End? ILM graciously provided us time with the movie magicians behind Pirates III -- including Oscar-winning Visual Effects Supervisor John Knoll, who supervised the shoot; Visual Effects Art Director Aaron McBride (pictured above) who designed some of Davy Jones's more memorable crewmen for this film; and CG Supervisor Joakim Arnesson, who oversaw the film's climactic maelstrom sequence. Visual Effects Supervisor John Knoll presented footage demonstrating the complexity of ILM's work on the film, whether environments (like the Tortuga Bay pirate cove) or characters (like Davy Jones (Bill Nighy) and his crew) or the combination of live-action with massive effects sequences, like the maelstrom battle at the finale -- which involved one of the biggest blue-screen shoots Knoll's ever seen, incorporating real water and wind effects on full-size sets. both Knoll and Pirates director Gore Verbinski are fans of incorporating real-world objects into effects shots -- a technique demonstrated by the before-and after shots shown where, in one case, a crew rams a prow on wheels out from the shore to get a real splash of sea water as it hits the surf -- seawater that's then draped around a computer-generated ship's bow for the final shot. Knoll also showed stuntmen knocked to and fro by 300,000 bouncing bright blue playset balls dropped onto on the pirate ship set -- and then the finished shot from the film that became, where the balls are replaced by the clattering crabs the gigantic sorceress Calypso dissolves into. The crabs are an illusion, but the bumps and bruises are real -- and, as Knoll points out, the shot's better for it.

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Knoll explained one of the biggest innovations in Pirates of the Caribbean: At World's End was a evolutionary leap in on-set motion-capture, meshing real actors and sets with the digitally-created dwellers of the deep like Davy Jones (Nighy) and his crew. The new ILM system -- called IMOCAP -- relies on actors wearing gray costume jumpsuits with distinctive black-and-white polygonal shapes placed on joints and other index points. More traditional motion capture, as used on Beowulf or The Polar Express, involves an extensive array of cameras set up in a curve that, as Knoll noted, " ... would have been way too much to bring to a location." ILM's advances in the underlying IMOCAP software mean that Knoll and his crew can get the data needed for motion capture on-set using as few cameras as possible, so their gray-suited actors can stalk the set, react and interact with stars like Depp, Bloom and Knightly before being transformed. "It's a suit, like motion capture, but it can happen anywhere. ..." (Knoll also let slip that the same technique is being used for Iron Man, coming in 2008) Demonstrating pre-effects footage of Nighy in his gray motion-capture jumpsuit working with the other actors on-set, Knoll observed how the system allows for a much more interactive, actor-led process: "It's live action; Bill Nighy really drives the performance. It all came about because Gore never felt like he'd seen a live action CGI character that was believable. "

Visual Effects Art Director Aaron McBride also spoke to director Verbinski's firm hand on the far-flung work of the visual effects team as he explained the conceptual art and thoughts behind some of Davy Jones's crew in the ship -- the half-human, half-sea creature pirates. I asked if any of the team's provisional designs were rejected because they would have posed too great a task for the FX crew, and McBride's answer was another glimpse into Verbinski's vision. "It was never a case of 'That's going to be really tough to do. ...' Actually, some of the tougher ones wound up being the ones that Gore would choose." McBride explained how the monster pirates were intentionally designed to look pained and mutated, not smooth or symmetrical: "One of the directives that Gore gave us is that he didn't want things to look too gimmicky; we needed to find interesting ways for sea life to intersect the human form. But one of the challenges was it couldn't be a whole piece; it couldn't be a whole shark, for example. It had to be piece of a shark that would be instantly recognizable as 'Oh, that guy's fused with a shark.' He didn't want them too evolved - and I think that was what he meant by 'too gimmicky." We had a (pirate) that was fused with a sea turtle -- and he looked too 'Draw me! I'm Tipsy the Turtle!' But (Verbinski chose) things that looked a little more accidental or haphazard, like they had evolved in a more uncomfortable way. More asymmetry and mutation, as opposed to evolution ... Gore was looking for characters that felt very accidental, like they had mutated in an erratic way. "

McBride and the other concept artists on the team looked at a wide and disgusting variety of visual inspirations: degenerative skin diseases, shellfish, other marine life and even autopsy photos. And yet, McBride notes, the team's execution kept Davy's crew from crossing the line between startling and shocking, between gruesome and gross, even with his team's most bizarre visions: "Nothing was ever really too unpleasant. As horrible as some of these guys looked, because Gore presented them in a very humorous way some times in the movie, that negated their shock value; the more gruesome they were, the more you'd believe them and take them seriously -- but also they were that much more funny when humorous things would happen to them in the film."

Also offering his take on the challenges of Pirates III was CG Supervisor Joakim Arnesson, an ILM veteran responsible for coordinating the final maelstrom battle sequence -- which incorporated over 300 visual effects shots, and took the team 8 months in and of itself. After crafting widescreen environments full of realistic water and wood but also fantastic visions, Arnesson sounds exhausted by his work for the sequence: "I was on it from its development to the bitter end ..." And, he also noted, it's not as if they could simply recycle prior work: "... we don't have a library of shots, we have a library of techniques." Those libraries of techniques -- and the data stores of the effects team -- were both stretched to nearly the breaking point by the challenges in Pirates of the Caribbean: At World's End. The climactic whirlpool at the finale required " ... trying to simulate a 2,000 foot wide maelstrom of water," a feat of computer effects engineering that required "... terabytes of data discs. There are a lot of steps, and they all add up to an enormous amount of data." Arnesson's been with ILM since 1996, and I asked him what the biggest change he's seen take place in the field in the past 11 years. To him, it wasn't any single he could name as having improved, like fire or water, but rather" ...the complexity of the work. We can show full CG shots. The work is more and more specialized." And, as a close to the day, Arnesson pointed out how every advance ILM makes is just to keep pace with the visions and desires of big-budget Hollywood, and he and his peers have to work harder with more equipment as the state of the art moves forward. Arnesson ruefully noted that, thanks to software improvements and faster computers, effects shots "... tend to look better now ... but they're not easier."