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One of the more essential expansions occurs when the Millennium Falcon first arrives at Cloud City. The original sequence is set at nightfall, with a limited shot of Bespin as seen from the Falcon's cockpit. What followed was a shot of the spacecraft touching down on a landing pad. ILM has now inserted several new shots between the original two: first, the Falcon soars through a corridor of buildings towards the horizon; then, as the freighter disappears behind a building, there is a cut to a new shot of the Falcon heading around the building towards camera and settling over the landing pad. During that 10-second scene, almost a quarter of Cloud City comes into view. Explains Empire and Jedi CG supervisor Tom Hutchinson, "First of all, we set up a 3-D re-creation of the city in three-space. Jonathan Rothbart set up some relatively low-res animatics for us, which we used as a template to plan our camera moves. After refining the move, we flew our 'virtual camera' through the City, then built in the detail and flew the vehicles along that trajectory. At times we did it back and forth."

Hutchinson and company also struggled to define what clouds look like as they head off into infinity from above and below in a very nonterrestrial perspective. "The clouds were strictly 2-D matte paintings on a disc in the background," Hutchinson reveals, "but we had to figure out what the horizon line looks like when you're on the edge of a disk in the sky. Fortunately, those shots are set at magic hour, and we get more caught up in the aesthetics and how pretty that time of night can be, so the lighting is more forgiving."

ILM's artists could not be so lenient for a newly created sequence that tracks a Twin-Pod Cloud Car - a red-hued scout ship - blazing a trail between the hovering city's towering spires at high noon. "Actually creating a full synthetic city on this scale is challenging," Hutchinson admits, "but the most difficult aspect is re-creating outdoor lighting. There is no existing computer graphics technology that can simulate the bounce light that you get out in the real world from the sun and buildings. People love to use ray-tracing to tackle that reflective light from the sky, but our environment was too big for the existing software. We had to simulate that look by hand-painting sunlight sources and shadows, and building it all up layer by layer. But we could only put so much detail into the buildings; otherwise, the city model would have gotten too big. So there's a compromise: we put less detail on the buildings that were furthest away. We see glimpses of the whole ground plane, with parks and cities, through the buildings. This was done using matte paintings painted onto an object connected to the 3-D model."

One of the more demanding examples of matching the revamped scenes with those of the original Empire arises after the camera has trailed the CG Cloud Car flying through the spires of Bespin; this cuts to an original establishing shot of Princess Leia, spied through the window of a matte-painted building as a Cloud Car model sails by. After Lucas effected his changes, however, the Cloud Car and the live-action plate of Leia in the window were the only elements remaining from the original effects shot. "There were two things that we thought could be improved on the original shot," Hull explains. "First, Leia's building is composed on the far right of the frame, which placed the emphasis elsewhere. Second, there is a skylight above Leia in the following shot, but it's not apparent in the original building design. So I composed her building into frame and redesigned it with a skylight on the top. For consistency, we didn't want to change many things. We kept most of the original matte painting while adding the building along with the Cloud Car in computer graphics."

Other challenges came to light in a new establishing shot of Darth Vader heading for his Imperial Shuttle after Lando Calrissian orders the evacuation of Cloud City. Once again, the CG shuttle in Empire had to precisely match the original miniature, which was previously seen only in the subsequent film, Return of the Jedi. The heretofore unseen evacuation not only gave ILM's effects artists an excuse to add several additional ships fleeing the city, but also offered them an opportunity to create an entirely new view of Bespin. Now, a loudspeaker blares Calrissian's command over footage combining real people reacting in the foreground (shot against blue-screen), and CG crowds running through massive CG architecture in the background.

The original interiors of Cloud City itself consisted primarily of setpieces - enclosed corridors and rooms - to help compensate for scheduling and financial limitations on Empire. For the re-do, Lucas decided to open those tight corridors up - literally. "George asked us to put windows in the enclosed hallways in a number of Cloud City shots," Carson explains. "There were also a number of shots of people running down hallways where there were a couple of windows with something hanging on the other side of the set to represent a skyline. In both cases, we've done some matte paintings to open those sets up and allow a better view of Cloud City.

"George felt that those tight environments needed a really airy feel, so we did about eight to 10 shots where he asked us to cut windows in the walls and put the city out back. He wanted more detail in the shots, so we've done matte paintings and added aerial cars to create sky traffic - anything to add more detail and more space."

Since these shots were originally photographed with a moving camera, ILM had to construct their matte-painted views of Cloud City in layers (such as multi-plane animation setups) in order for the backgrounds to parallax in a believable fashion. "We've built some pretty complicated environments," Hutchinson adds. "Most of those CG mattes were 2 1�2-D: we painted matte paintings on layered 'cards' in the computer to get the perspective switch as we moved the camera around."

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