Bert Van Brande and his animation pipeline team came upon the idea of splitting the scenes into manageable chunks. Scene files are put together in integration where they are using significantly lighter rigs for the characters and the train. Before the facial capture is applied, the integrated body performances are submitted for approval (into animation), and the scenes split before transferring the files to Maya. If the characters are constrained to the train, each split file would carry with it the motion from whatever node the characters were constrained to. All of these splits had to be recomposed into a single movie file for review by Bob.

After struggling through the process of using multiple image planes of each split in our render, character setup TD Amy Hronek came up with the Render Compositing Tool. This used Z-depth to automatically render and composite all the splits at once. It was a breakthrough that solved a plethora of problems. Now several artists could work on splits independently, and a single artist could render and composite each split in a final render for Bob to review.

Background Kids
There was an ongoing effort throughout production to seek simplifications that would drive the costs down. Given the amount of attention and effort put into our hero kids, it was decided at bid-time that the background kids would be plug-and-play straight out of integration. There was certainly no budget for any animation work on the extra characters, but I knew they would stand out like a sore-thumb if we mixed them in with our heroes. I proposed that we set them up as “bobble-heads,” where we only see the tops of their heads moving above the seat-backs. We could animate and refine a library of cycles that could be plugged into any shot that required seeing them. Bob agreed to try this simplification, but after presenting a few tests he thought that the kids were simply too disengaged from the surrounding action. At this point, production editorial began specifying specific performance beats for each one of the background kids. This made them prominent in the shots, so a certain level of animation became necessary. If the kids were bouncing on the seats, or running across the aisles it was necessary to do the 12% time scale (to correct the adult-to-child time space) and apply the supplemental animation where necessary to fill in the gaps. There were also the contact issues with seats, props and other characters in the scene. Unfortunately, the background faces were only rigged for basic expression changes, partly due to the simplified face topology and patch layout. We could move the eyeballs, but none of the procedural shape changes described above were rigged into these characters. Therefore, animation effort was put into animating faces away from camera wherever possible. None of this work was accounted for in our bids, and each hour spent on background kids would need to be reclaimed on other sequences in the future. The numbers were being watched very carefully.

Director Robert Zemeckis changed his mind about the look of Lonely Boy during the production, making it necessary to rework the rigging for his character.

Lonely Boy Sequence (LB)
Number of Shots: 41
November 20, 2003-May 12, 2004

The Lonely Boy sequence is where we pick up Billy from “the other side of the tracks.” The original “Lonely Boy” was a different character design rigged with the same arsenal of animation controls featured in our other hero characters.

When Bob saw the first motion tests with this character, he was concerned that this particular “Billy” was miscast. Instead, he cited a specific background kid that he believed would fit the bill perfectly. Our setup crew went to work immediately in an attempt to rig the alternate model to make him a full-featured character. It took several weeks to produce marginally-acceptable deformations in the face, but nothing like the results we were getting with the other heroes. It turns out that the face topology was very different, and our best efforts could not overcome the fact that the patch layout in the background models did not follow the natural contours of the face. They were never intended for high-level performance rigging, and optimized as background characters instead. This rig would need a lot more work before it was fully-functional. The first step was to redistribute the isopharm layout in modeling, and then back to rigging for another round.

Unfortunately we couldn’t wait. While this rework was underway, we continued to move shots though the department using the existing rig. Thankfully, Billy’s performance is muted during the first half of the film, and he doesn’t show much expression until we approach the North Pole. By the time he launched into song, we were ready to go with the new character. Lead animator Keith Kellog had been working with the rig and preparing expressions for the pose library so that a smooth transition could be made the first time Billy opened his mouth to speak/sing.

Hot Chocolate Sequence (HC)
Number of Shots: 32
December 10, 2003-May 7, 2004

The dance sequence was choreographed in production editorial, and characters placed in the scene to achieve the desired composition for each shot. Since shot composition was king, integration’s challenge was to make all the characters fit without interpenetrating. The hot chocolate cart was designed to travel straight down the center aisle, but there was very little clearance, especially when the waiters were hanging off the sides. When the cart spins, it simply didn’t fit so the aisle had to be widened. When the waiters ran up the walls and around the ceiling we discovered that they were penetrating into the ceiling so we had to expand the size of the car. It was a house-of-cards in that performances of the other characters would no longer fit the expanded environment and had to be adjusted to accordingly. Again, these tasks were not figured into the budget so we knew that the numbers would have to be reclaimed elsewhere.

Tightly choreographed performances were captured separately, so characters never responded to each other as they would if they were captured together. Actually, there was plenty of interaction between them in that they interpenetrated horribly. It was a giant puzzle with eight waiters, two chefs, the conductor and a hot chocolate cart all packed into the center aisle, and it was a different puzzle on every frame because of the broad dance movements. The offsets on all of those bodies and limbs had to be adjusted frame-by-frame to be sure they cleared each other (and the props) in a dance that was packed into a sardine can. It was a huge relief to the crew each time the waiters hopped onto the tables because that meant they were out of the aisle!